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

Christina has four daughters, and each of her daughters has a brother. How many children does Christina have?

A network of 20 x 10 squares is given to you.

Can you calculate how many unique squares and rectangles can be formed combining two or more individual squares ?

Find the value of "?" in the ball picture Riddle below:

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

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?

An octopus has 8 legs. A hippogriff has 6 legs and 2 pairs of wings. A sphinx has 6 legs and one pair of wings. Now we have all 3 kinds and a total of 18 insects in a cage. We have a total of 118 legs and 20 pairs of wings. How many insects do we have of each kind?

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.

There are two candles. Both will only burn exactly for an hour. How will you use these two candles to measure forty-five minutes?

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