What is common among 11, 69, and 88?

A rain drop fell from one leaf to another leaf and lost 1/4th of its volume. It then fell to another leaf and lost 1/5th of the volume. It again fell on another leaf and lost 1/5th of the volume.



This process kept repeating till it fell on the last leaf losing 1/75th of its volume.



Can you calculate the total percentage of loss from the initial volume when the drop has fallen to the last leaf accurate up to two decimal places?

If,

6 / 7 = 2
3 / 9 = 7
8 / 2 = 6

Then

4 / 5 = ?

If two's company, and three's a crowd, then whats four and five ?

Move three sticks of the spiral below to form a square.

I drive at an average speed of 30 miles per hour to the railroad station each morning and catch my train. On a particular morning, there was a lot of traffic and at the halfway point, I had averaged only 15 miles per hour. How fast must I drive for the rest of the way to catch my train?

I travel all around the world but always stay in the corner. What am I?

What is the fewest number of coins that would be required in order to make sure each and every coin touches exactly three other coins?

Can you place six matchsticks in a manner that each of the matchsticks is in touch with the other five matchsticks?

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