When Jack was six years old he hammered a nail into his favourite tree to mark his height. Ten years later at age sixteen, Jack returned to see how much higher the nail was. If the tree grew by five centimetres each year, how much higher would the nail be?

There is a circular car race track of 10km. There are two cars, Car A and Car B. And they are at the exact opposite end to each other. At Time T(0), Both cars move toward each other at a constant speed of 100 m/seconds. As we know both cars are at the same speed they will always be the exact opposite to each other.
Note, at the center, there is a bug which starts flying towards Car A at time T(0). When the bug reaches car B, it turns back and starts moving towards the car A. The speed of bug is 1m/second. After 5 hours all three stop moving.
What is the total distance covered by the bug?

If eleven plus two equals one, what does nine plus five equal?

Can you find out the smallest number that can be conveyed as the sum of three squares in three unique ways?

Count the number of triangles in the picture below:

You can hear me, but you can't touch or see me.

What am I?

Can you find the thief by just looking at the picture below?

What has many teeth, but cannot bite?

Which alphabet letter is a question?

What can jump higher than a building?