If 21x = 79x, what is the value of x?

An evil man kidnapped someone and made them take one of two pills. One was harmless, but the other was poisonous. Whichever pill the victim took, the kidnapper took the other one. The victim took their pill with water and died. The kidnapper survived. How did the kidnapper get the harmless pill?

I have lakes with no water, mountains with no stone and cities with no buildings. What am I?

Why is a river so rich ?

Women do it once a year after they turn 19 but men get to do it only once in a lifetime. What is it?

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.

What is the centre of gravity?

How many cubic feet of dirt are in a hole of one foot deep, three feet long, and two feet wide?

I went to the bookshop and spent one-half of the money that was in my purse.

When I came out, I found that I had as many cents as I had dollars and half as many dollars as I had cents when I went in. Find the money in my purse when I entered the store.

I can write cow in 13 letters.

Can You?