What does this simple rebus mean?

If six children and two dogs were under an umbrella, how come none of them got wet?

What is in seasons, seconds, centuries and minutes but not in decades, years or days?

In a box, there is a jumble of 7 red balls, 6 blue balls, 5 green balls, and 4 yellow balls. What is the minimum number of balls, will you have to pick up so that you have at least 4 balls of the same colour?

What is more useful when it is broken?

The dirtier I get, the whiter I look. Who am I?

A man has to get a fox, a chicken, and a sack of corn across a river.

He has a rowboat, and it can only carry him and one other thing.
If the fox and the chicken are left together, the fox will eat the chicken.
If the chicken and the corn are left together, the chicken will eat the corn.

How does the man do it?

The more you take me, the more you leave me behind.
Who Am I?

If 1+9+8=1, what is 2+8+9?

why number 8549176320 is one of a kind?