probability problems - Wikitechy https://www.wikitechy.com/interview-questions/tag/probability-problems/ Interview Questions Mon, 06 Sep 2021 06:46:53 +0000 en-US hourly 1 https://wordpress.org/?v=6.9 https://www.wikitechy.com/interview-questions/wp-content/uploads/2025/10/cropped-wikitechy-icon-32x32.png probability problems - Wikitechy https://www.wikitechy.com/interview-questions/tag/probability-problems/ 32 32 A brother and sister appear for an interview against two vacant posts in an office. The probability of the brother’s selection is 1/5th and that of the sister’s selections is 1/3rd. What is the probability that one of them is selected ? https://www.wikitechy.com/interview-questions/probability/a-brother-and-sister-appear-for-an-interview-against-two-vacant-posts-in-an-office-the-probability-of-the-brothers-selection-is-1-5th-and-that-of-the-sisters-selections-is-1-3rd-what-is-the-prob/ https://www.wikitechy.com/interview-questions/probability/a-brother-and-sister-appear-for-an-interview-against-two-vacant-posts-in-an-office-the-probability-of-the-brothers-selection-is-1-5th-and-that-of-the-sisters-selections-is-1-3rd-what-is-the-prob/#respond Wed, 18 Aug 2021 02:10:04 +0000 https://www.wikitechy.com/interview-questions/?p=2051

A brother and sister appear for an interview against two vacant posts in an office. The probability of the brother’s selection is 1/5th and that of the sister’s selections is 1/3rd. What is the probability that one of them is selected ?

A. 1/5

B. 2/5

C. 1/3

D. 2/3

Answer : B. 2/5

Explanation:

Probability that only one of them is selected = (prob. that brother is selected) × (prob. that sister is not selected) + (Prob. that brother is not selected) × (Prob. that sister is selected)

Hence, Required Probability = 1/5 x 2/3 + 4/5 x 1/3
= 2/15 + 4/15
= 6/15
= 2/5.

]]> https://www.wikitechy.com/interview-questions/probability/a-brother-and-sister-appear-for-an-interview-against-two-vacant-posts-in-an-office-the-probability-of-the-brothers-selection-is-1-5th-and-that-of-the-sisters-selections-is-1-3rd-what-is-the-prob/feed/ 0 Tickets 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 ? https://www.wikitechy.com/interview-questions/probability/tickets-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/ https://www.wikitechy.com/interview-questions/probability/tickets-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/#respond Wed, 18 Aug 2021 01:48:27 +0000 https://www.wikitechy.com/interview-questions/?p=2032

Tickets 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. 8/12

D. 9/20

Answer : D. 9/20…

Explanation:

Here, S = {1, 2, 3, 4, 19, 20}.
Let E = event of getting a multiple of 3 or 5
= {3, 6 , 9, 12, 15, 18, 5, 10, 20}.
P(E) = n(E) / n(S)
= 9/20

]]> https://www.wikitechy.com/interview-questions/probability/tickets-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/feed/ 0 In a box, there are 8 red, 7 blue and 6 green balls. One ball is picked up randomly. What is the probability that it is neither red nor green ? https://www.wikitechy.com/interview-questions/probability/in-a-box-there-are-8-red-7-blue-and-6-green-balls-one-ball-is-picked-up-randomly-what-is-the-probability-that-it-is-neither-red-nor-green/ https://www.wikitechy.com/interview-questions/probability/in-a-box-there-are-8-red-7-blue-and-6-green-balls-one-ball-is-picked-up-randomly-what-is-the-probability-that-it-is-neither-red-nor-green/#respond Wed, 18 Aug 2021 01:43:40 +0000 https://www.wikitechy.com/interview-questions/?p=2029

In a box, there are 8 red, 7 blue and 6 green balls. One ball is picked up randomly. What is the probability that it is neither red nor green ?

A. 1/3

B. 3/4

C. 7/19

D. 8/21

E. 9/21

Answer : A. 1/3

Explanation:

Total number of balls = (8 + 7 + 6) = 21.
Let E = event that the ball drawn is neither red nor green
= event that the ball drawn is blue.
n(E) = 7
P(E) = n(E)/n(S)
= 7/21
= 1/3

]]> https://www.wikitechy.com/interview-questions/probability/in-a-box-there-are-8-red-7-blue-and-6-green-balls-one-ball-is-picked-up-randomly-what-is-the-probability-that-it-is-neither-red-nor-green/feed/ 0 Two cards are drawn together from a pack of 52 cards. The probability that one is a club and one is a diamond ? https://www.wikitechy.com/interview-questions/probability/two-cards-are-drawn-together-from-a-pack-of-52-cards-the-probability-that-one-is-a-club-and-one-is-a-diamond/ https://www.wikitechy.com/interview-questions/probability/two-cards-are-drawn-together-from-a-pack-of-52-cards-the-probability-that-one-is-a-club-and-one-is-a-diamond/#respond Wed, 18 Aug 2021 01:34:03 +0000 https://www.wikitechy.com/interview-questions/?p=2024

Two cards are drawn together from a pack of 52 cards. The probability that one is a club and one is a diamond ?

A. 13/51

B. 1/52

C. 13/102

D. 1/26

Answer : C. 13/102…

Explanation:

n(S) = Total number of ways of drawing 2 cards from 52 cards = 52C2.
Let E = event of getting 1 club and 1 diamond.
We know that there are 13 clubs and 13 diamonds in the total 52 cards.
Hence, n(E) = Number of ways of drawing one club from 13 and one diamond from 13 = 13C1 × 13C1 = 13/102
P(E) = n(E)/n(S)
= (13C1 × 13C1) / 52C2
= 13/102.

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