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

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

Solve the mathematical equation in the picture below.

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

How many people must be gathered together in a room, before you can be certain that there is a greater than 50/50 chance that at least two of them have the same birthday?

The product of three consecutive numbers is 7980.
Then the sum of these consecutive numbers would be?

The square root of number 121 is "11". What is the square root of the number "12345678987654321."?

A man has eighty-one cows ( numbered 1,2,3...81 as such). The beauty is that cow no. 1 gives 1ltr of milk, cow no. 2 gives 2ltrs of milk and so on. The man wants to equally distribute the cows among his nine sons so that each one of them gets the same quantity of milk.

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?

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