What is the fastest way to double your money?

Find The Next Number In The Sequence

30 10 15 13 0 16 -15 ?

Find three whole, positive numbers that have the same answer when multiplied together as when added together.

How many triangles can you find in this given picture?

Why Aeroplane windows are round?

In front of you, there are 9 coins. They all look absolutely identical, but one of the coins is fake. However, you know that the fake coin is lighter than the rest, and in front of you is a balance scale. What is the least number of weightings you can use to find the counterfeit coin?

A horse was tied to a rope 5 meters long and the horses food was 15 meters away from the horse. How did the horse reach the food?

Find the next number in the series

12, 20, 40, 72, 116, 172 ?

What is the word or phrase?

Can you count the number of quadrilaterals in the picture below?