If you had a pizza with crust thickness 'a' and radius 'z', what's the volume of the pizza?

Find the missing number in the image below.

I have an apple tree , number of apple in this tree get doubles every week.

On 30th week , the tree gets completely filled with apples :-)



Can you tell me , on what week does my tree is half covered with apples ?

What is the fewest number of coins that would be required in order to make sure each and every coin touches exactly three other coins?

What is black when you buy it, red when you use it, and gray when you throw it away?

What is always in front of you but can’t be seen?

What number when divided in half becomes zero?

It's pretty hard to give up.
If you remove a part of it, you will be left with a bit.
Even if you remove another part, the bit still remains.
Remove one more and it still remains.

What is it?

Can you find the least possible number such that

If the number is divided by 3, it gives the remainder of 1;
If the number is divided by 4, it gives the remainder of 2;
If the number is divided by 5, it gives the remainder of 3;
If the number is divided by 6, it gives the remainder of 4.

Find out a multi-digit number that if multiplied by the number 9 or any of its multiplications products (i.e. 18, 27, 36, 45,..) will result in the multiplication factor repeated (n) number of times.