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

What is the unique property of the following words ?
* Revive
* Banana
* Grammar
* Voodoo
* Assess
* Potato
* Dresser
* Uneven

Why is it very easy to weigh a fish?

What is a word made up of 4 letters, yet is also made up of 3. Sometimes is written with 9 letters, and then with 4. Rarely consists of 6, and never is written with 5.

I have no doors but I have keys, I have no rooms but I have space, you can enter but you can’t leave! What am I?

I have lakes with no water, mountains with no stone and cities with no buildings. What am I?

Can you solve this picture maths equation?

Decode below rebus
D
N
A
T
S , D

An equation has been laid down using a few matchsticks. However, as you can see, the equation is not correct. Can you correct the equation if you are allowed to add or remove 5 matchsticks?

What 5-letter word typed in all capital letters can be read the same upside down?