Take away my first letter, then take away my second letter. Then take away the rest of my letters, yet I remain the same. What am I?

2, 3, 5, 9, 17, _ What is the next number in the sequence?

I am a mother. However, I never give birth.

I am a father. However, I never nurse my children.

Wandering is not possible for me, but standing still happens occurs rarely.

Who am I?

Prove that the below maths equation is true.

8 + 8 = 91

Eight Chelsea player makes the following statements :

1. Seven of us are lying here.
2. Six of us are lying here.
3. Five of us are lying here.
4. Five of us are lying here.
5. Four of us are lying here.
6. Three of us are lying here.
7. My name is Torres.
8. My name is Lampard.

The last two are Lampard and Torres or maybe Torres and Lampard.
So can you deduce which of the last two is Lampard or Torres?

Can you think of any three-dimensional shape that comprises of exactly two surfaces?

Why do we preferably have round manhole covers and not square ones?

Can you count the number of triangles in the given picture?

On a magical land of Mexico , all the animal in the land are rational.

There are 10 tigers and one goat.
Tiger can eat goat but since it's a magical land , the tiger who eats the goat , turns into goat and then can be eaten by the remaining tiger(s).

If we leave them for some time then how many goat and tiger will be there , when we come back ?

How will you measure 15 minutes using two hourglasses of 7 minutes and 11 minutes respectively?