I’m light as a feather, yet the strongest person can’t hold me for five minutes. What am I?

I have a hole in my back and legs I lack.
I live where I can’t breathe and I eat without teeth.
What am I?

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

Twenty frogs are sitting on a log floating on the surface of a river. Two of them decide to jump off into the water.

How many frogs are there on the log at this moment?

A wooden log balances equally on the scales when weighed with three-quarters of a pound and three-quarters of a wooden log.

Can you calculate the weight of the entire wooden log?

I am weightless, but you can see me. Put me in a bucket, and I'll make it lighter. What am I?

I am under you when I am whole.
I shift above you if you remove the first letter.
I come all around you if you remove the second as well.

Can you tell me who I am?

If eleven plus two equals one, what does nine plus five equal?

I am the fastest animal but cannot climb the tree. What am I?

Can you write down eight eights so that they add up to one thousand?