What is both possible and impossible at the same time?

Replace each alphabet with the number (1-9) to make the below equation correct.

AB * C = DE - F = GH / I

First, think of the colour of clouds. Next think the colour of snow. Last, think of the colour of the moon. Now, what do cows drink?

10+10 and 11+11 can give you the same answer.

Explain how?

A pond had 60 fish, out of which, all but 20 died.
How many fishes are now present in that pond?

What common phrase is represented by the below lines

Easy going:
Weak, 'I'm going.'
Tough, 'I'm staying.'

Medium going:
Weak, 'I'm going.'
Tough, 'I'm staying.'

Tough going:
Weak, 'I can't do it, I'm staying!'
Tough, 'Let's get going.'

I am looking for a word that change both gender and number when i add the letter 'S'.

What Word am I Looking For ?

What brings you down but never up?

In a jungle where there are no street lights or any other artificial source of lights, I notice a black snake crossing the road.
How did I get sight of the snake?

A boy purchased a book from a bookkeeper and gave him $100.
The cost of the book is $50 but the bookkeeper has no change, so he gets the change from the next shop and returns the boy his $50.

After some time the next shopkeeper came with the $100 note and told the bookkeeper that the note was a fraud, so he took the money back.

How much loss did the bookkeeper face?