It walks on 4 when its young, walks on 2 when it's older, and walks on 3 when its very old?

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?

Look at this sequence from top to bottom. What is the next number in the sequence?
1
11
21
1211
111221
312211

I am the beginning of the end, and the end of time and space. I am essential to creation, and I surround every place. What am I?

That attorney is my brother, testified the accountant.

But the attorney testified he didn't have a brother.

Who is lying?

Find the next number in the series below

21 32 54 87 131 ?

There is a shop where written:
Buy 1 for $1
10 for $2
100 for $3
I needed 999 and still only paid $3. How could this be financially viable for the shop-keeper?

Twenty frogs are sitting on a log floating on the surface of a river. Two of them decide to jump off into the water.

How many frogs are there on the log at this moment?

There is a family that live in a round house. The two parents go out for a movie and leave a babysitter to watch their son. They come back and the kid was not there. Some one kidnapped him. The maid said she was cleaning in a corner. The cook said he was making pizza. The babysitter said she was getting a board game. Who kidnapped him.

Spelt forwards I’m what you do every day, spelled backwards I’m something you hate. What am I?