You are given a cube that is made with the help of 10x10x10 smaller cubes summing up to a total of 1000 smaller cubes. You are asked to take off one layer of the cubes.
How many remain now?

After teaching his class all about Roman numerals (X = 10, IX=9 and so on) the teacher asked his class to draw a single continuous line and turn IX into 6. The teacher's only stipulation was that the pen could not be lifted from the paper until the line was complete.

An express train takes 3 seconds to enter the tunnel which is 1 km long.
If it is travelling at 120 km an hour, how long will it take to pass completely through the tunnel?

Can you find the thief by just looking at the picture below?

If 21x = 79x, what is the value of x?

I have Rs.50 and I spend it in the way as below.

It belongs to you, but other people use it more than you do. What is it?

If eleven plus two equals one, what does nine plus five equal?

I have no doors but I have keys, I have no rooms but I have space, you can enter but you can’t leave! What am I?

In case you were starting to feel confident, this one was meant for third graders in Vietnam. The answer is 66, but we don't blame you for scratching your head about how they got there.