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

Explain how?

What has lots of eyes, but can’t see?

What occurs twice in a week, once in a year but never in a day?

Find the next number in the series below

21 32 54 87 131 ?

When 99 is considered higher than 100?

Assume there are approximately 5,000,000,000 (5 billion) people on Earth. What would you estimate to be the result, if you multiply together the number of fingers on every person's left hand? (For the purposes of this exercise, thumbs count as fingers, for five fingers per hand.) If you cannot estimate the number then try to guess how long the number would be.

At the local model boat club, four friends were talking about their boats.

There were a total of eight boats, two in each colour, red, green, blue and yellow. Each friend owned two boats. No friend had two boats of the same colour.

Alan didn't have a yellow boat. Brian didn't have a red boat but did have a green one. One of the friends had a yellow boat and a blue boat and another friend had a green boat and a blue boat. Charles had a yellow boat. Darren had a blue boat, but didn't have a green one.

Can you work out which friend had which coloured boats?

There was a competition where the contestants had to hold something. At the end of the event, the winner was a person who had no hands or feet. What was it that the contestants had to hold?

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?

I add 5 to 9 and get 2. The answer is correct, so what am I?