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

I have teeth but i don't bite. Who Am I ?

I am the one who remains awake when you sleep. But I need to rest when you awake. Who Am I?

While house hunting in London, I came across a very good leasehold property Discussing the lease the landlady told me:

'The property was originally on a 99 years lease and two-thirds of the time passed is equal to four-fifths of the time to come. Now work it out for yourself and see how many years are to go!

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

There are forty elephants and they have forty-fore heads. How can this be possible?

Rectify the following equality 101 - 102 = 1 by moving just one digit.

Can you count the number of children in the picture below

There is a box. The area of its top is 240 square units, the area of the front is 300 square units and the area of the end is 180 square units.

Can you calculate the dimensions of this box with the given data?

John was working on a Chemical Mixture whose weight comprise 90% liquid and 10% solid. The total weight of the mixture is 20 pounds. After a while, John noticed that some of the liquid evaporated and now the liquid comprises just 50% of the weight.

What is the weight of the chemical mixture now?