What occurs twice in a week, once in a year but never in a day?

A shepherd had 18 sheep, out of which, all but ten died.

Can you tell us how many sheep was he left with?

If a wheel has 54 spokes, how many spaces are there between the spokes?

Our product and our sum always give the same answer. Who are we?

If we change the South-East direction into North and North-East into West and all others similarly.
Can you find out which direction will be in the place of South-West direction?

You have 10 balls with you. A friend of yours out of nowhere asks you to place those ten balls in five lines such that each of the lines has exactly 4 balls on them. He needs to check your intelligence. Prove him by doing the task.

Solve the puzzle by telling what does below picture means.

What have one eye but still cannot see?

What has 13 hearts but no other organs?

I have holes on the top and bottom. I have holes on my left and on my right. And I have holes in the middle, yet I still hold water. What am I?