1If an operation can be performed in different ways, and another independent operation can be performed in different ways, what is the total number of ways to perform both operations together?
principles of counting
Easy
A.
B.
C.
D.
Correct Answer:
Explanation:
According to the fundamental principle of multiplication, if two operations are independent, the total number of ways to perform both is the product of their individual ways ().
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2If an event can occur in ways and a second event can occur in ways, but both cannot occur simultaneously, in how many ways can either of the events occur?
principles of counting
Easy
A.
B.
C.
D.
Correct Answer:
Explanation:
According to the fundamental principle of addition, if two events are mutually exclusive (cannot occur simultaneously), the total number of ways for either to occur is .
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3What is the formula for the number of permutations of distinct objects taken at a time, denoted by ?
numerical permutation(formation of numbers and sum of numbers)
Easy
A.
B.
C.
D.
Correct Answer:
Explanation:
The formula for permutation calculates the number of ways to arrange objects chosen from distinct objects, given by .
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4How many 3-digit numbers can be formed using the digits 1, 2, and 3 without repeating any digit?
numerical permutation(formation of numbers and sum of numbers)
Easy
A.6
B.3
C.9
D.27
Correct Answer: 6
Explanation:
Since repetition is not allowed, the number of ways to arrange 3 digits in 3 places is .
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5In how many different ways can the letters of the word 'CAT' be arranged?
alpha permutation(rearrangement of words and rank of a word)
Easy
A.9
B.12
C.3
D.6
Correct Answer: 6
Explanation:
The word 'CAT' has 3 distinct letters. The number of arrangements is .
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6What is the total number of ways to arrange distinct letters in a row?
alpha permutation(rearrangement of words and rank of a word)
Easy
A.
B.
C.
D.
Correct Answer:
Explanation:
The number of ways to arrange distinct items in a straight line is factorial, written as .
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7What is the formula for the number of ways to arrange distinct objects around a circular table?
circular arrangement
Easy
A.
B.
C.
D.
Correct Answer:
Explanation:
In a circular arrangement, fixing one object gives a reference point for the others. Hence, the remaining objects can be arranged in ways.
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8In how many ways can 4 people sit around a circular table?
circular arrangement
Easy
A.24
B.4
C.6
D.12
Correct Answer: 6
Explanation:
Using the circular permutation formula , for , the number of ways is .
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9In how many ways can 3 identical letters be dropped into 4 distinct letterboxes?
distribution based questions
Easy
A.
B.
C.
D.
Correct Answer:
Explanation:
Each of the 3 letters has 4 choices of letterboxes. Thus, the total number of ways is .
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10What is the formula for combinations, , representing the number of ways to select objects from distinct objects?
formation of committee
Easy
A.
B.
C.
D.
Correct Answer:
Explanation:
Combinations represent selection where order does not matter. The formula is .
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11In how many ways can a committee of 2 members be selected from a group of 4 people?
formation of committee
Easy
A.6
B.4
C.8
D.12
Correct Answer: 6
Explanation:
The number of ways to select 2 people out of 4 is given by .
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12How many distinct straight lines can be drawn by joining any two points from a set of non-collinear points?
geometry based problems
Easy
A.
B.
C.
D.
Correct Answer:
Explanation:
A straight line requires exactly 2 points. Choosing 2 points from non-collinear points is a combination problem, yielding lines.
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13Which of the following describes the correct range for the probability of any event ?
concept of probability
Easy
A.
B.
C.
D.
Correct Answer:
Explanation:
Probability represents the likelihood of an event occurring, ranging from 0 (impossible event) to 1 (certain event) inclusive.
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14What is the sum of the probabilities of all the mutually exclusive and exhaustive elementary events of an experiment?
concept of probability
Easy
A.Infinity
B.1
C.0
D.0.5
Correct Answer: 1
Explanation:
The sum of the probabilities of all possible distinct outcomes in a sample space is always exactly 1.
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15If two events and cannot occur at the same time, what are they called?
classification of events
Easy
A.Independent events
B.Mutually exclusive events
C.Exhaustive events
D.Dependent events
Correct Answer: Mutually exclusive events
Explanation:
Mutually exclusive events are events that cannot happen simultaneously, meaning .
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16What is the formula for the conditional probability of event given that event has already occurred, denoted as ?
conditional probability
Easy
A.
B.
C.
D.
Correct Answer:
Explanation:
The conditional probability is defined as the probability of the intersection of A and B divided by the probability of the given event B.
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17If events and are independent, what is equal to?
conditional probability
Easy
A.
B.
C.
D.
Correct Answer:
Explanation:
For independent events, the occurrence of one does not affect the other, so their joint probability is the product of their individual probabilities.
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18What is the probability of getting a 'Head' when a fair, unbiased coin is tossed once?
problems based on coins dices and cards
Easy
A.
B.
C.
D.1
Correct Answer:
Explanation:
A coin has 2 possible outcomes (Head, Tail). The probability of getting a Head is 1 favorable outcome out of 2 total outcomes.
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19What is the probability of rolling an even number on a standard 6-sided die?
problems based on coins dices and cards
Easy
A.
B.
C.
D.
Correct Answer:
Explanation:
A die has 3 even numbers (2, 4, 6) out of 6 possible outcomes. The probability is .
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20If a single card is drawn from a standard deck of 52 playing cards, what is the probability that it is an Ace?
problems based on coins dices and cards
Easy
A.
B.
C.
D.
Correct Answer:
Explanation:
There are 4 Aces in a deck of 52 cards. The probability is , which simplifies to .
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21There are 4 different routes to travel from City A to City B, and 3 different routes to travel from City B to City C. In how many ways can a person travel from City A to City C and return back to City A without using the same route twice?
Principles of counting
Medium
A.84
B.72
C.144
D.12
Correct Answer: 72
Explanation:
To go from A to C, the person has choices. To return from C to A without using the same routes, they have $2$ choices left from C to B and $3$ choices left from B to A, giving choices. By the fundamental principle of counting, total ways = .
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22How many 4-digit even numbers can be formed using the digits 1, 2, 3, 4, and 5 without repetition?
Numerical permutation
Medium
A.120
B.60
C.24
D.48
Correct Answer: 48
Explanation:
For the number to be even, the units place must be filled with either 2 or 4 (2 options). After fixing the units place, the remaining 3 places can be filled by the remaining 4 digits in ways. Total even numbers = .
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23What is the sum of all 3-digit numbers that can be formed using the digits 1, 2, and 3 without repetition?
Numerical permutation
Medium
A.1221
B.1332
C.1233
D.1320
Correct Answer: 1332
Explanation:
The number of 3-digit numbers is . Each digit appears in each place value (hundreds, tens, units) exactly times. The sum of the digits is . The sum of all numbers is .
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24In how many ways can the letters of the word 'SUCCESS' be arranged so that all the 'S's are together?
Alpha permutation
Medium
A.20
B.420
C.120
D.60
Correct Answer: 60
Explanation:
Treat the three 'S's as a single unit (SSS). The letters to arrange are (SSS), U, C, C, E. This gives 5 units. The letter 'C' repeats twice. The number of arrangements is .
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25What is the dictionary rank of the word 'LATE' if all permutations of its letters are arranged alphabetically?
Alpha permutation
Medium
A.15
B.12
C.13
D.14
Correct Answer: 14
Explanation:
Alphabetical order of letters: A, E, L, T. Words starting with A: . Words starting with E: . The next words start with L. The first is LAET (13th). The next is LATE (14th). Hence, its rank is 14.
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26In how many ways can 4 men and 4 women sit around a circular table such that no two men sit together?
Circular arrangement
Medium
A.576
B.24
C.144
D.288
Correct Answer: 144
Explanation:
The correct option follows directly from the given concept and definitions.
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275 friends are to be seated around a circular table. In how many ways can they be seated if two specific friends, A and B, refuse to sit next to each other?
Circular arrangement
Medium
A.36
B.24
C.48
D.12
Correct Answer: 12
Explanation:
Total ways to seat 5 people around a table is . If A and B sit together, treat them as one unit. The 4 units can be seated in ways, and A and B can swap in ways. Ways they sit together = . Ways they do NOT sit together = .
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28In how many ways can 8 identical chocolates be distributed among 3 children such that each child receives at least one chocolate?
Distribution based questions
Medium
A.28
B.21
C.56
D.35
Correct Answer: 21
Explanation:
This is equivalent to finding the positive integer solutions to . The formula is , where and . Thus, .
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29A committee of 4 members is to be formed from 5 men and 4 women. In how many ways can this be done if the committee must contain exactly 2 women?
Formation of committee
Medium
A.120
B.60
C.80
D.45
Correct Answer: 60
Explanation:
To have exactly 2 women in a 4-member committee, we must select 2 women from 4, and 2 men from 5. Number of ways = .
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30A group of 5 people is to be chosen from 6 men and 4 women. In how many ways can the group be formed so that men are in the majority?
Formation of committee
Medium
A.186
B.150
C.246
D.120
Correct Answer: 186
Explanation:
Men are in majority if there are 3, 4, or 5 men.
Case 1 (3M, 2W): .
Case 2 (4M, 1W): .
Case 3 (5M, 0W): .
Total ways = .
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31How many triangles can be formed by joining 10 points in a plane, if exactly 4 of these points are collinear?
Geometry based problems
Medium
A.120
B.116
C.110
D.114
Correct Answer: 116
Explanation:
Total possible triangles from 10 points without restriction is . However, the 4 collinear points cannot form a triangle. The number of degenerate triangles from these is . Valid triangles = .
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32Find the number of diagonals in a regular decagon (a polygon with 10 sides).
Geometry based problems
Medium
A.25
B.45
C.20
D.35
Correct Answer: 35
Explanation:
The formula for the number of diagonals in a polygon with sides is . For a decagon, . Diagonals = .
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33What is the probability that a randomly chosen leap year has 53 Sundays?
Concept of probability
Medium
A.
B.
C.
D.
Correct Answer:
Explanation:
A leap year has 366 days, which is exactly 52 weeks and 2 extra days. The extra days can be (Sun, Mon), (Mon, Tue), (Tue, Wed), (Wed, Thu), (Thu, Fri), (Fri, Sat), or (Sat, Sun). Out of 7 possible pairs, 2 contain a Sunday. Thus, the probability is .
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34If A and B are two independent events such that and , what is the value of ?
Classification of events
Medium
A.0.5
B.0.6
C.0.3
D.0.4
Correct Answer: 0.5
Explanation:
For independent events, . Using the addition theorem: .
.
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35A family has 2 children. Given that at least one of them is a boy, what is the probability that both children are boys?
Conditional probability
Medium
A.
B.
C.
D.
Correct Answer:
Explanation:
The sample space for two children is {BB, BG, GB, GG}. The condition 'at least one is a boy' restricts the sample space to {BB, BG, GB}. Among these 3 equally likely outcomes, only 1 outcome is {BB}. The probability is .
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36Two standard dice are rolled. Given that the sum of the numbers appearing on them is 8, what is the probability that at least one die shows a 3?
Conditional probability
Medium
A.
B.
C.
D.
Correct Answer:
Explanation:
Outcomes where the sum is 8 are (2,6), (3,5), (4,4), (5,3), and (6,2), which is a total of 5 outcomes. The outcomes with at least one 3 are (3,5) and (5,3). Thus, the probability is .
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37Three unbiased coins are tossed simultaneously. What is the probability of getting at most two heads?
Problems based on coins dices and cards
Medium
A.
B.
C.
D.
Correct Answer:
Explanation:
When 3 coins are tossed, the total number of outcomes is . 'At most two heads' means 0, 1, or 2 heads. The only outcome NOT included is 3 heads (HHH). So, the probability is .
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38Two fair dice are thrown together. What is the probability that the product of the numbers obtained is an even number?
Problems based on coins dices and cards
Medium
A.
B.
C.
D.
Correct Answer:
Explanation:
The product is even if at least one die shows an even number. The easier way is to find the probability that both are odd and subtract from 1. The probability of an odd number on one die is . The probability of odd on both is . The probability of an even product is .
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39Two cards are drawn at random from a standard deck of 52 cards without replacement. What is the probability that both cards are Kings?
Problems based on coins dices and cards
Medium
A.
B.
C.
D.
Correct Answer:
Explanation:
There are 4 Kings in a 52-card deck. The probability of drawing a King first is . The probability of drawing a second King from the remaining 51 cards is . Total probability = .
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40A card is drawn from a well-shuffled pack of 52 cards. What is the probability that it is either a Heart or a Face card?
Problems based on coins dices and cards
Medium
A.
B.
C.
D.
Correct Answer:
Explanation:
Let H be Heart and F be Face card. , (J, Q, K in 4 suits), and (J, Q, K of Hearts). Using .
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41What is the sum of all distinct 5-digit numbers that can be formed using the digits 1, 2, 3, 4, and 5 without repetition?
numerical permutation(formation of numbers and sum of numbers)
Hard
A.3,999,960
B.1,555,550
C.3,888,860
D.3,333,300
Correct Answer: 3,999,960
Explanation:
To find the sum of all such numbers, we use the formula: Sum = (Sum of all digits) \times (n-1)! \times (111...n \text{ times}). The sum of digits is . There are 5 digits, so . The multiplier is $11111$. Sum = .
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42How many 5-digit numbers divisible by 3 can be formed using the digits 0, 1, 2, 3, 4, 5 without repetition?
numerical permutation(formation of numbers and sum of numbers)
Hard
A.216
B.192
C.120
D.240
Correct Answer: 216
Explanation:
A number is divisible by 3 if the sum of its digits is a multiple of 3. The total sum of the given 6 digits is 15. To select 5 digits whose sum is a multiple of 3, we must leave out a digit that is a multiple of 3 (either 0 or 3). Case 1: Leave out 0. Digits: {1,2,3,4,5}. Number of arrangements = . Case 2: Leave out 3. Digits: {0,1,2,4,5}. The first digit cannot be 0 (4 choices), remaining 4 places can be filled in ways. . Total = .
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43What is the rank of the word 'TOUGH' if all permutations of its letters are arranged in alphabetical (dictionary) order?
alpha permutation(rearrangement of words and rank of a word)
Hard
A.72
B.84
C.89
D.90
Correct Answer: 89
Explanation:
The letters in alphabetical order are G, H, O, T, U. Words starting with G, H, or O are . Next come words starting with T. T followed by G, H are . Total so far = 84. Next is TO. TOG and TOH give . Total = 88. The next word is TOUGH. Its rank is .
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44In how many ways can the letters of the word 'MISSISSIPPI' be arranged such that no two vowels are adjacent?
alpha permutation(rearrangement of words and rank of a word)
Hard
A.14,700
B.34,650
C.7,350
D.1,050
Correct Answer: 7,350
Explanation:
The correct option follows directly from the given concept and definitions.
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45If 8 distinct people sit around a circular table, in how many ways can they be seated such that two specific people, A and B, do NOT sit diametrically opposite each other?
circular arrangement
Hard
A.4,320
B.5,040
C.720
D.3,600
Correct Answer: 4,320
Explanation:
Total unrestricted circular arrangements of 8 people = . Now, find the cases where A and B sit opposite each other. Fix A at any seat (1 way). B must sit opposite to A (1 way). The remaining 6 people can sit in the remaining 6 seats in ways. Thus, ways they do not sit opposite = .
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466 men and 6 women sit around a circular table. What is the probability that no two women sit together?
circular arrangement
Hard
A.
B.
C.
D.
Correct Answer:
Explanation:
Total unrestricted seating arrangements = . For the favorable outcome, first seat the 6 men in a circle: ways. This creates 6 gaps between the men. The 6 women can be seated in these 6 gaps in ways. Favorable ways = . Probability = .
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47In how many ways can 10 identical apples be distributed among 4 children such that each child gets at least 1 apple, but no child gets more than 4 apples?
distribution based questions
Hard
A.44
B.40
C.84
D.56
Correct Answer: 44
Explanation:
Let be the apples for child , . Let , so , and . By stars and bars, total solutions without the upper bound = . We subtract cases where any . If , let . Then , which has solutions. Since there are 4 variables, total violations = . Valid distributions = .
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48What is the number of arrangements of 6 distinct letters into their respective 6 distinct addressed envelopes such that exactly 2 letters are placed in their correct envelopes?
distribution based questions
Hard
A.180
B.270
C.135
D.45
Correct Answer: 135
Explanation:
The correct option follows directly from the given concept and definitions.
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49A committee of 6 members is to be formed from 5 teachers and 8 students. Teacher A refuses to be on the committee if Student B is included. In how many ways can the committee be formed?
formation of committee
Hard
A.1,056
B.1,386
C.1,716
D.330
Correct Answer: 1,386
Explanation:
Total unrestricted ways to form the committee = . The number of committees that include both Teacher A and Student B requires choosing 4 more members from the remaining 11 people: . The valid number of committees = Total ways - restricted ways = .
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50A committee of 5 is formed from 6 men and 4 women. Given that the committee contains at least 1 woman, what is the probability that it contains at least 2 women?
formation of committee
Hard
A.
B.
C.
D.
Correct Answer:
Explanation:
Total ways to choose 5 from 10 is . Ways with 0 women = . Ways with at least 1 woman = . Ways with exactly 1 woman = . Ways with at least 2 women = . Required conditional probability = .
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51What is the maximum number of intersection points produced by 8 circles and 6 straight lines in a plane?
geometry based problems
Hard
A.167
B.145
C.182
D.120
Correct Answer: 167
Explanation:
Maximum intersections occur when every pair of figures intersects at the maximum possible points. 8 circles intersect each other in points. 6 lines intersect each other in points. 8 circles and 6 lines intersect each other in points. Total = .
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52How many triangles can be formed by joining the vertices of a regular 12-sided polygon such that no side of the triangle is a side of the polygon?
geometry based problems
Hard
A.220
B.120
C.112
D.144
Correct Answer: 112
Explanation:
The formula for the number of triangles sharing no side with a regular -sided polygon is . Substituting , we get .
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53Two real numbers and are chosen uniformly and independently at random from the interval . What is the probability that and ?
concept of probability
Hard
A.
B.
C.
D.
Correct Answer:
Explanation:
The sample space is the unit square in the first quadrant, area = 1. The region is a quarter-circle of area . The region is a right triangle of area . We want the region inside the quarter-circle but outside the triangle. The intersection area is . Since the total area is 1, the probability is .
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54Let and be two independent events such that and . Find the value of .
classification of events
Hard
A.0.8
B.0.6
C.0.4
D.0.3
Correct Answer: 0.6
Explanation:
For independent events, . The formula for union is . Substituting the values: .
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55A diagnostic test for a disease has a 99% accuracy rate for both positive and negative results. The prevalence of the disease in the population is 1 in 1000. If a randomly selected person tests positive, what is the approximate probability they actually have the disease?
conditional probability
Hard
A.9.0%
B.50.0%
C.0.1%
D.99.0%
Correct Answer: 9.0%
Explanation:
Let be disease, be positive test. , , , . By Bayes' Theorem: or 9.0%.
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56Urn A contains 3 red and 4 black balls. Urn B contains 5 red and 6 black balls. One ball is transferred from Urn A to Urn B, and then two balls are drawn simultaneously from Urn B. If both drawn balls are red, what is the probability that the transferred ball was red?
conditional probability
Hard
A.
B.
C.
D.
Correct Answer:
Explanation:
Let be transferring Red () and be transferring Black (). If , Urn B has 6R, 6B. . If , Urn B has 5R, 7B. . By Bayes' Theorem, .
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57Three machines A, B, and C produce 40%, 30%, and 30% of a factory's total output, respectively. The defect rates are 2%, 3%, and 4%. If an item is drawn at random and found to be non-defective, what is the probability it was produced by Machine B?
conditional probability
Hard
A.
B.
C.
D.
Correct Answer:
Explanation:
Let be non-defective. . , , . By Bayes' Theorem: .
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58A fair coin is tossed 10 times. What is the probability of getting exactly 4 heads, given that at least 2 heads occurred?
problems based on coins dices and cards
Hard
A.
B.
C.
D.
Correct Answer:
Explanation:
Total outcomes = . The event 'at least 2 heads' (let's call it ) excludes 0 heads and 1 head. . The event 'exactly 4 heads' (let's call it ) is a subset of . . Thus, .
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59Three standard 6-sided dice are rolled simultaneously. What is the probability that the sum of the numbers showing on the upper faces is exactly 14?
problems based on coins dices and cards
Hard
A.
B.
C.
D.
Correct Answer:
Explanation:
We need the number of solutions to where . Let , so where . Without restrictions, solutions = . Subtract cases where any . Since , one variable can exceed 5. Let , so , giving . Since there are 3 variables, subtract . Valid outcomes = . Probability = .
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60Four cards are drawn at random from a standard 52-card deck. What is the probability of getting exactly two pairs (e.g., two 8s and two Kings)?
problems based on coins dices and cards
Hard
A.
B.
C.
D.
Correct Answer:
Explanation:
The correct option follows directly from the given concept and definitions.