A firefighter stood on the middle rung of a ladder,
spraying water on a burning house.
He then climbed up 6 rungs
before the heat of the flames caused him to come down 10 rungs.
After some minutes he was able to climb 18 rungs
to the very top of the ladder.
How many rungs did the ladder have?
The firefighter is standing on the middle rung.
He goes up 6 rungs so he is now at M+6,
He now goes down 10 rungs so he is now at M-4
He now goes up 18 rungs and reaches the top
So from the middle he goes 14 rungs to top.
So 14 rungs from the top, 14 rungs from the bottom and the middle rung.