Can you find out which number multiplied by itself will give the output as 12345678987654321?

Can you find the missing number in the third row?
35 20 14
27 12 18
5 2 ?

Can you think of any three-dimensional shape that comprises of exactly two surfaces?

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

Replace the 'X' with any mathematical symbol to make the expression equal to 111.

18 X 12 X 2 X 3 = 111

I want to fill my bucket using both cold and hot water.
I have two taps for both cold and hot water. The hot water tap fills the bucket in exact 6 hours and the cold water tap fills the bucket in exact 4 hours.
I turn both of them simultaneously but I forgot to turn off another tap which removes the water out of the bucket. This tap can empty the bucket in 12 hours.

How Long will it take to fill the bucket?

John can fit six large chocolate boxes or nine small chocolate boxes into a carton. How many cartons will he require to put sixty-six chocolate boxes into?

In a school, there are four subjects. Seventy percent of students study English, seventy five percent of students study Science, eighty five percent of students study Mathematics and eighty percent of students study Spanish.

Can you calculate the percentage of students that study all four subjects?

Can you make numbers like 24, using numbers 3,3,7 & 7 with any arithmetic operator?

I am a prime number.
The double of myself is equal to the square of me.

which number am I?