# How does Tarun find the sum so quickly?

148 views

Ms. Anuska asked the class to see if they could find the sum of the first 50 odd numbers. As everyone settled down to their addition, Tarun ran to her and said, "The sum is 2,500." Ms. Anuska thought, "Lucky guess," and gave him the task of finding the sum of the first 75 odd numbers. Within 20 seconds, Tarun was back with the correct answer of 5,625.

How does Tarun find the sum so quickly?

posted Jun 25, 2015

+1 vote

The sum of first 'n' odd numbers is (n*n).
So, the sum of first 50 odd numbers is (50*50) i.e. 2550.
The sum of first 75 odd numbers is (75*75) i.e. 5625.

Similar Puzzles

It looks so ordinary and plain that you would think nothing is wrong with it. In fact nothing is wrong with it!
Still this paragraph is highly unusual.
Study it and think about it, but you may not find anything odd. If you work at it a bit, you might find out. Try to do it without any coaching.

This is an unusual paragraph.
I'm curious how quickly you can find out what is so unusual about it?
It looks so plain you would think nothing was wrong with it! In fact, nothing is wrong with it! It is unusual though. Study it, and think about it, but you still may not find anything odd. But if you work at it a bit, you might find out!
Try to do so without any coaching!