A certain street contains 100 buildings. They are numbered from 1 to 100. How many 9's are used in these numbers?

No matter how little or how much you use me, you change me every month. What am I?

Can you find out the remainder when 3^300 is divided by 5?

A famous swimmer can swim downstream in a lake in exactly 40 minutes with the lake current.
He can swim upstream in that lake in exactly 60 minutes against the lake current.
The length of the lake is 2 km.

How long he can cover the distance of one side at a still lake with no current?

Solve the equation by replacing the alphabet with numbers.

MOM + MOM + NO = BOOK=

Can you solve the tricky chess rebus puzzle below by ciphering the hidden meaning?

What does the following BrainBat signifies?

ABCDEFGHIJKLMNOPQRSTUVWYZ

QQQQQQQQQQQQQQQQQQQQQQQQQ.

Jenifer is learning to drive her car. She went down a one way lane and in the wrong direction. But she do not break any law.

How come ?

It can be easily calculated that the digits 0 to 9 can be arranged into 3628800 distinct ten-digit numbers.

But do you know how many of these numbers are prime?

They came out at night, without being called.
They lost at day, without being stolen.
Who are they?