Solution:

0! or cos(0)

Solution:

Kid1, he was left with one rock.

Solution:

Four

three placed flat on the table in a triangle(touching each other) and put the fourth one on top of them in the middle.

Solution:

The two babies are two of a set of triplets(or even more)

Solution:

1

(Only Me)

Solution:

Suicide

Solution:

The clerk said that every day the password is CHANGED. Changed is the password.

Solution:

25%

Suppose every item is priced at $100. On 20% discount, the price will become $80. Now he must add $20 to each item for original price which is 25% of $80.

Solution:

Birbal drew another line that was larger than the pre-drawn line. Now the pre drawn line was smaller.

Solution:

I filled a glass full of water and held it over my head for 20 minutes.