Replace the question mark with the correct number.

Which is heavier: a ton of bricks or a ton of feathers?

I have an eye but still cannot see.

Who am I?

Two guards were on duty outside a barracks. One faced up the road to watch for anyone approaching from the North. The other looked down the road to see if anyone approached from the South. Suddenly one of them said to the other, "Why are you smiling?"

How did he know his companion was smiling?

Who always enjoys poor health?

Find the number of squares in the below-given picture.

Why is it very easy to weigh a fish?

What is always in front of you but can’t be seen?

Using eight eights and addition only, can you make 1000?

Can you find the key in the picture below?