Birthday Dilemma

Number Theory Level 2

Al and Sal are 2 friends. Find the probability that their birthday falls on different dates. The probability can be expressed as a/b ( a and b are co-primes). Then find (a+b). NOTE: Ignore a leap year.


The answer is 729.

D K by D K , 23, India

This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try refreshing the page, (b) enabling javascript if it is disabled on your browser and, finally, (c) loading the non-javascript version of this page . We're sorry about the hassle.

2 solutions

Ajith Kumar
Mar 3, 2014

The Probability that their birthdays lie on the same date is 1/365.Therefore,the probability that they lie on different dates is 1- 1/365.= 364/365. their sum is 364+465=729

1 Helpful 0 Interesting 0 Brilliant 0 Confused

I think it'll be 364+365=729 in the last line.

Raiyun Razeen - 7 years, 3 months ago
Arijit Banerjee
Mar 3, 2014

First of all any 1 of them can have his birthday in 365 ways so his probability is 365/365 =1 .Now for his 2nd friend there is only 364 options left so his probability of getting a date is 364/365. so 1* 364/365 = 364/365 .then 364+365 =729

0 Helpful 0 Interesting 0 Brilliant 0 Confused

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...