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

What does below Rebus say?

XLR8

What is the centre of gravity?

How high do you have to count before you use the letter “a” in the English spelling of the whole number?

There is a box full of marbles,
all but two are blue,
all but two are green,
and all but two are red.

How many marbles are in the box?

Find three numbers such that When we multiply three numbers, we will get the prime numbers. The difference between the second and the first number is equal to the third and second.

A boy collects white seashells from the sea and brings them home every night. When he has enough of them, he decides to sell them to a trader.

The trader is ready to buy the shells and he asks the boy about the quantity. At this, the boy starts calculating. He has a giant box that contains 3 mini boxes. Two of them have another mini box inside. If the giant box can hold 50 shells, how many brown shells can he sell to the trader?

How many cubic feet of dirt are in a hole of one foot deep, three feet long, and two feet wide?

Replace the question mark with the correct number.

There was an aeroplane crash, every single person died, but two people survived. How is this possible?