TIFR CSE 2018 | Part A | Question: 6

Question

What is the minimum number of students needed in a class to guarantee that there are at least $6$ students whose birthdays fall in the same month ?

• A. $6$
• B. $23$
• C. $61$
• D. $72$
• E. $91$

Comments

The concept of the Pigeonhole principle is kind of similar to the concept of deadlock where we need to calculate a minimum number of resources.

Answer 1

By pigeon hole principal we can ensure that in 61 we will have atleast 6 student having birthday on same month

n=km+1 k=5, m=12

Answer 2

You have to visualise it

Then you dont need any formula

You need at least 6 students na, whose birthday fall on same month

Go

And first get me 5 students per month

like 5 students who have birthday in Jan

5 student who have birthday in Feb

.

.

.

5 students who have birthday in December

Good question: Why I chose 5 in every month

Because, I am just short of 1 student ( let it be any month) I dont care
 

What I did was simply

$(5*12)+1 = 61$

Imagine

Just imagine

Dialogue: From Krish movie, No copyright infringement intended