A bus driver, you, is out on school run early Friday morning.
Unlike other school days with heavy traffic, 7 kids are in the bus.
At the first bus stop, 5 kids get on, 2 get off. Later 9 get on, 11 get off. And at the last bus stop, 4 get on, none gets off.
How old is the bus driver?
You have 20 apples in a basket. 20 children come to you, each asking for an apple.
You want to give each of them an apple and still keep one inside the basket.
How will you do this?