By removing one matchstick and adding one matchstick, can you convert the word "ZOO" to an animal name?

When my father was 31 I was 8. Now he is twice as old as me. How old am I?

Count the number of triangles in the below picture?

There’s a one-story house in which everything is yellow. Yellow walls, yellow doors, yellow furniture. What colour are the stairs?

John and his wife were living in a rural place. On a particular day, John's wife fell ill and he called the local doctor. When the doctor picked up, he said, "Doctor, my wife is ill. She might have appendicitis."

"This can't be possible! I took out her appendix two years ago myself," the doctor explained.

When diagnosed, John's wife was found to have appendicitis. How can this be possible?

What will be the best approach to finding all the prime numbers less than 75 that leave an odd reminder when we divide them with 5?

This is a classy optical illusion puzzle. What more you can find except bricks in the image below?

A Doctor always sneezes before the rain. Doctor sneezes, Will it rain?

A number with an interesting property:

When I divide it by 2, the remainder is 1.
When I divide it by 3, the remainder is 2.
When I divide it by 4, the remainder is 3.
When I divide it by 5, the remainder is 4.
When I divide it by 6, the remainder is 5.
When I divide it by 7, the remainder is 6.
When I divide it by 8, the remainder is 7.
When I divide it by 9, the remainder is 8.
When I divide it by 10, the remainder is 9.

It's not a small number, but it's not really big, either.
When I looked for a smaller number with this property I couldn't find one.

Can you find it?

What goes up but never comes down?