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

Replace the question mark with the correct number in below Picture:

Christina, Allison and Lena are 3 daughters of John a well-known Mathematician, When I asked John the age of their daughters. He replied "The current age of her daughters is prime. Also, the difference between their ages is also prime."

How old are the daughters?

Can you calculate the probability of getting a sum of six when a dice is thrown twice?

Find the number of squares in the below-given picture.

Can you find the ages of a son, father and grandfather based on the following facts?
The sum of the ages of grandfather, father and son is 140 years.
The age of the son in months is the same as the grandfather in years.
The age of the son in days is the same as the father in weeks.

'S' refers to the number of seconds in a day and 'H' refers to the number of hours in ten years. Which quantity out of these two is greater?

John replied, when asked how old he was. In 2 years he will be twice as old as he was five years ago.' How old is he ?

Replace the (?) with the correct mathematical signs to make the expression equal to 59.

18 ? 12 ? 4 ? 5 = 59

Can you write down eight eights so that they add up to one thousand?