Question

# On a new year day every student of a class sends a card to every other student. The postman delivers 600 cards. The number of students in the class are :

- 42
- 34
- 25
- 52

Hint:

### For example there are 2 students A and B, A will give card to B and vice versa.

Thus each student will give card to other students except himself.

## The correct answer is: 25

### Total cards delivered = 600

Lets assume number of students = n

Each students will give card to (n-1) students

{(n-1),(n-1),(n-1) ............ (n-1)} n times

Total cards = n(n-1) = 600

The number of students in the class are 25.

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