Can you find out who is the kidnapper in below Picture and why, Explain ?

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.

If,
9 * 8 * 7 = 65
8 * 7 * 6 = 50
7 * 6 * 5 = 37

Find
6 * 5 * 4 = ?

Count the number of balls in picture below:

What has 88 keys?

What number does the below three word/phrase identify and why?
1. Deck
2. Year
3. Singing in the Rain

I have a five and a three-gallon jar. Assuming there is an infinite supply of water, how can I measure one-gallon water?

What does this rebus mean?

O
N
C
E
TIME

I have a mouth but I don't eat.
I have a bank but have no money.
I have a bed but i dont sleep.
I wave but have no hands.

Who Am I ?

There is one thing that goes round the house and also inside the house but never even share a brief touch. What is it?