What is the fastest way to double your money?

What is the largest amount of money that you can possess in change and still if someone asks you for a dollar, you won't be able to give?

Count the squares in the matchstick puzzle below?

Two boys wish to cross a river. The only way to get to the other side is by boat, but that boat can only take one boy at a time. The boat cannot return on its own, there are no ropes or similar tricks, yet both boys manage to cross using the boat.

How?

Why is it very easy to weigh a fish?

How can you take 2 from 5 and leave 4?

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

You are provided with a grid (as shown in the picture). Can you fill the squares with numbers 1-8 in a manner that none of the two consecutive numbers are placed next to each other in any direction (vertically, horizontally or diagonally?)

Which English verb becomes past tense just by rearranging the letters?

How can you make the following equation true by drawing only one straight line: 5+5+5=550 ?