How can you write nineteen in a manner that if we take out one, it becomes twenty?

If there are fifteen crows on a fence and the farmer shoots a third of them, how many crows are left?

A mules travels the same distance daily.
I noticed that two of his legs travels 10km and the remaining two travels 12km.
Obviously two mules legs cannot be a 2km ahead of the other 2.

The mules is perfectly normal. So how come this be true ?

In my garden, I have many trees but only one of them is the mango tree. In these mango trees, there are some mangoes(as expected).

But after a strong wind, there are neither mangoes on the tree nor on the ground. Explain?

What 4-letter word can be written forward, backward or upside down, and can still be read from left to right?

I am the one who remains awake when you sleep. But I need to rest when you awake. Who Am I?

Two boys were admitted to a school. When the headmaster asks them about their parents, they tell him that they have same parents (father and mother). On further inquiry, it turns out that they both share the same date for their birthday.

"Are you twins," ask the headmaster.
"No," replies the boys.

Is it possible?

Do you know who was buried in John's tomb?

What has 88 keys?

Make a sentence consisting of three words that have the whole alphabet.