Question

Birthaay Paradox: Take 2 Homework. Unanswered At the end of June, a bunch of customers all having birthdays in July enter a bakery to order cakes for their July birthday celebrations. How many such customers must there be so that there is at least a 50% chance (>=.5 probability) that at least two of them were born on the same day in July (ignore the year). Assume that there are no other customers in the store and that there are no concerns about social distancing etc. Select an answer and submit. For keyboard navigation, use the up/down arrow keys to select an answer. a 5 b 7 с 9 d 11 e 13 f 15 g 17 h 19 .- 21 i 23

Answer 1

Birthday Paradox:

The answer is b.7.

In the classic Birthday Paradon problem where the probability of two people having same birthday in a year is calculated, the probability for n people and 365 days comes out to be: 1- P(365,n)/365. In the given problem since the number of days is 31, it can be calculated by replacing 365 by 31. Hence the probability will be:

1- P(31,n)/31 Where P(n,r) denotes permutation.

When the value of n is 7 the probability is 0.518 which is the required answer.

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