When I had already gone down 7 of the steps of the staircase that overlooks the street I ran into the neighbor's son who climbed the steps two at a time so that when I still had 4 steps left to get down the boy had already climbed All the stairs. What agility! I thought. For every step that I go under it goes up two.
How many steps does the ladder have?
The ladder must have 22 steps because from the data of the problem we know that when the boy has climbed the whole ladder I still have 11 steps (7 + 4). Since he climbs two steps for each one that I climb, the whole staircase must have twice the 11 steps that I am missing or 22.