Explanation:By definition of factorials, . This is a convention that makes formulas like and work consistently.
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2In how many different ways can the letters of the word "OPTICAL" be arranged so that the vowels always come together?
A.120
B.576
C.720
D.4320
Correct Answer: 720
Explanation:The word is OPTICAL. Total letters = 7. Vowels = O, I, A (3). Consonants = P, T, C, L (4). Treat vowels as 1 unit. Total units = 4 (consonants) + 1 (vowel group) = 5. Arrangements = . Internal arrangement of vowels = . Total = .
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3Evaluate .
A.120
B.720
C.240
D.30
Correct Answer: 120
Explanation:
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4How many words can be formed by using all letters of the word "MISSISSIPPI"?
Explanation:If , then either or . Here , so . We need to find . .
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6In how many ways can 5 people be seated around a circular table?
A.120
B.24
C.60
D.12
Correct Answer: 24
Explanation:The number of circular permutations of distinct objects is . Here, .
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7How many 3-digit numbers can be formed from the digits 2, 3, 5, 6, 7 and 9, which are divisible by 5 and none of the digits is repeated?
A.5
B.10
C.15
D.20
Correct Answer: 20
Explanation:To be divisible by 5, the unit digit must be 0 or 5. Available digits: 2, 3, 5, 6, 7, 9. Only 5 is available. Unit place fixed (1 way). Remaining 2 places filled by remaining 5 digits in ways. .
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8Find the number of diagonals in a decagon (10-sided polygon).
A.35
B.45
C.90
D.20
Correct Answer: 35
Explanation:Number of diagonals in an -sided polygon = or . For : .
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9A committee of 5 is to be formed out of 6 men and 4 women. In how many ways can this be done if at least 2 women are included?
10In a party, everyone shakes hands with everyone else. If there are 66 handshakes, how many people are there?
A.11
B.12
C.13
D.10
Correct Answer: 12
Explanation:Number of handshakes for people is . . . Since is positive, .
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11How many different necklaces can be made from 10 different beads?
A.
B.
C.
D.
Correct Answer:
Explanation:For a necklace, clockwise and anticlockwise arrangements are considered the same. Formula: . Here, .
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12There are 4 different routes from A to B and 3 different routes from B to C. In how many ways can a person go from A to C via B?
A.7
B.12
C.64
D.1
Correct Answer: 12
Explanation:By the Fundamental Principle of Counting (Multiplication Rule): ways.
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13In how many ways can 5 prizes be distributed among 4 students if each student may get any number of prizes?
A.
B.
C.
D.
Correct Answer:
Explanation:Each of the 5 prizes can go to any of the 4 students. .
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14How many triangles can be formed by joining 12 points, 7 of which are collinear?
A.220
B.35
C.185
D.175
Correct Answer: 185
Explanation:Total triangles = . Triangles lost due to collinear points = . Result = = .
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15If , find .
A.5
B.6
C.7
D.8
Correct Answer: 6
Explanation:. We can estimate or factorize. . So .
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16What is the rank of the word "CAT" in a dictionary?
A.1
B.3
C.5
D.6
Correct Answer: 1
Explanation:Alphabetical order of letters: A, C, T. Words starting with A: . Words starting with C: Next is A, then T. So CAT is the first word starting with C. Rank = .
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17In how many ways can 3 boys and 3 girls sit in a row so that boys and girls alternate?
A.36
B.72
C.18
D.12
Correct Answer: 72
Explanation:Two cases: BGBGBG or GBGBGB. Case 1: . Case 2: . Total = .
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18Find the number of parallelograms that can be formed from a set of 4 parallel lines intersecting another set of 3 parallel lines.
A.6
B.12
C.18
D.9
Correct Answer: 18
Explanation:To form a parallelogram, we need 2 lines from the first set and 2 from the second. .
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19How many 4-digit numbers can be formed using the digits 0, 1, 2, 3, 4 without repetition?
Explanation:Using the formula for the number of terms in a multinomial expansion ( where terms. .
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21In how many ways can 6 distinct books be arranged on a shelf?
A.120
B.720
C.36
D.6
Correct Answer: 720
Explanation:Arrangement of distinct items = . .
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22A box contains 2 white balls, 3 black balls and 4 red balls. In how many ways can 3 balls be drawn from the box, if at least one black ball is to be included in the draw?
A.64
B.129
C.84
D.45
Correct Answer: 64
Explanation:Total balls = 9. Total ways to select 3 = . Ways to select 3 with NO black ball (only from 6 W/R) = . At least 1 black = Total - No black = .
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23Given 5 flags of different colours, how many different signals can be generated if each signal requires the use of 2 flags, one below the other?
36In a leap year, find the probability that there are 53 Sundays.
A.1/7
B.2/7
C.3/7
D.53/366
Correct Answer: 2/7
Explanation:Leap year = 366 days = 52 weeks + 2 days. The extra 2 days can be (Sat,Sun), (Sun,Mon), (Mon,Tue)... There are 7 combos. Sundays appear in (Sat,Sun) and (Sun,Mon). 2 favorable outcomes out of 7.
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37Two cards are drawn together from a pack of 52 cards. The probability that one is a spade and one is a heart is:
A.3/20
B.29/34
C.47/100
D.13/102
Correct Answer: 13/102
Explanation:Total ways . Favorable: 1 spade from 13 () and 1 heart from 13 (). . Prob = .
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38A bag contains 6 white and 4 black balls. Two balls are drawn at random. Find the probability that they are of the same colour.
A.1/2
B.7/15
C.8/15
D.1/9
Correct Answer: 7/15
Explanation:Total ways . Same colour means (2 White) OR (2 Black). . Prob = 21/45 = 7/15.
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39For independent events A and B, ?
A.
B.
C.
D.
Correct Answer:
Explanation:This is the definition of independent events.
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40A problem is given to three students whose chances of solving it are 1/2, 1/3 and 1/4 respectively. What is the probability that the problem will be solved?
A.1/4
B.1/24
C.3/4
D.23/24
Correct Answer: 3/4
Explanation:P(Problem Solved) = . . Result = .
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41If , and , find .
A.0.9
B.0.7
C.0.1
D.0.8
Correct Answer: 0.7
Explanation:.
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42Conditional probability is given by:
A.
B.
C.
D.
Correct Answer:
Explanation:Formula for conditional probability, provided .
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43Two dice are thrown. Find the probability that the product of the numbers appearing is odd.
A.1/2
B.1/4
C.3/4
D.5/36
Correct Answer: 1/4
Explanation:Product is odd only if both numbers are odd. Odd numbers on a die: {1,3,5} (3 numbers). Total outcomes = 36. Favorable outcomes = . Prob = 9/36 = 1/4.
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44What is the probability of drawing an Ace from a deck of cards?
A.1/52
B.4/52
C.1/26
D.12/52
Correct Answer: 4/52
Explanation:There are 4 aces in a deck (Spade, Club, Heart, Diamond). 4/52 = 1/13.
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45Tickets numbered 1 to 20 are mixed up and then a ticket is drawn at random. What is the probability that the ticket drawn has a number which is a multiple of 3 or 5?
A.1/2
B.2/5
C.8/20
D.9/20
Correct Answer: 9/20
Explanation:Multiples of 3: {3, 6, 9, 12, 15, 18} (6). Multiples of 5: {5, 10, 15, 20} (4). Common (15): 1. Total = . Prob = 9/20.
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46The odds in favor of an event are 3:5. The probability of the event occurring is:
A.3/5
B.5/3
C.3/8
D.5/8
Correct Answer: 3/8
Explanation:Odds in favor = . Probability = . Here, .
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47Two events A and B are such that , and . Then A and B are:
A.Mutually Exclusive
B.Independent
C.Dependent
D.Exhaustive
Correct Answer: Independent
Explanation:Since , the occurrence of B does not affect A. Thus, they are independent.
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48A card is drawn from a pack of cards. Find the probability that it is a King or a Red card.
50A jar contains 3 red marbles and 7 green marbles. If one marble is drawn, returned, and then a second marble is drawn, what is the probability that both are red?
A.9/100
B.9/90
C.1/10
D.3/10
Correct Answer: 9/100
Explanation:With replacement, events are independent. . .
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