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

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

Which country gets ill every time?

You are in a land where thirty men and two women were dressed in classic black and white dresses.
They begin to fight as soon as any of them move.

Where are you?

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?

Jigsaw captured 100 people and make them stand in a circle and all these people are labelled as Person1, Person2, Person3... Person100. He made them play a crazy game in which Person 1 shot Person 2 and pass the gun to the next person and so on until one stands alive.

Which person will survive in the end?

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

A number can be multiplied by multiple of nine
i.e 9 18 27 36 45 ...

and the resulting number consist of only one digit.

Can you identify the number ?

What is the four-digit number in which the first digit is one-third the second, the third is the sum of the first two, and the last is three times the second?

I throw two dice simultaneously.

What is the probability of getting a sum as 9 of the two numbers shown?