The square root of number 121 is "11". What is the square root of the number "12345678987654321."?

John replied, when asked how old he was. In 2 years he will be twice as old as he was five years ago.' How old is he ?

Can you arrange four 9's and use at most 2 math symbols, to make the total 100?

A man is walking down a road with a basket of eggs. As he
is walking he meets someone who buys one-half of his eggs
plus one-half of an egg.
He walks a little further and meets another person who buys
one-half of his eggs plus one-half of an egg.
After proceeding further he meets another person who buys
one-half of his eggs plus one half an egg. At this point, he
has sold all of his eggs, and he never broke an egg.
How many eggs did the man have to start with?

A mile-long train is moving at sixty miles an hour when it reaches a mile-long tunnel. How long does it take the entire train to pass through the tunnel?

I am an odd number. Take away a letter and I become even. What number am I?

A Shopkeeper collects 71 rupees in the form of 20 paisa and 25 paisa.
He collects a total of 324 coins.

Can you tell me how many number of 20-paisa and 25-paisa he got?

Find three whole, positive numbers that have the same answer when multiplied together as when added together.

Can you write down eight eights so that they add up to one thousand?

Can you find out the smallest number that can be conveyed as the sum of three squares in three unique ways?