Question

Kiteretsuki builds a robot to help him paint a fence. The robot has a paint roller of width 1 foot, that works like a ball-point pen, so it has a steady flow of ink. Kiteretsuki sets the robot to work and leaves but doesn't realize that the robot has a programming error.

It paints one foot of the fence from left to right, then stops and paints a foot in the right to left direction. It then starts moving from left to right again, but this time moving two feet instead of one. However, after this, it only moves back to its previous position. The robot carries on in this fashion, increasing its reach by 1 foot every left to right movement and then returning to its previous starting point.
If Kiteretsuki returns after the robot have moved a total of 11 times, how many inches of the fence has the robot painted in that time?​

Answer 1

72 inches

Explanation:

Due to the programming error, the robot first moves to the right and then to the left. The second time it moves to the right, it increases its distance by 1 foot to the right and then turns back and moves to the left, reaching the starting position again.

The patterns is as follows:

move 1: moves to the right by 1 foot.

moves 2: moves to the left.

moves 3: moves to the right by 2 feet.

moves 4: moves to the left

moves 5: moves to the right by 3 feet.d

moves 6: moves to the left

moves 7: moves to the right by 4 feet.

moves 8: moves to the left

moves 9: moves to the right by 5 feet.

moves 10: moves to the left

moves 11: moves to the right by 6 feet.

We see that in the end, the robot has managed to only move 6 ft. Since 1 ft = 12 inches, 6 ft = 6* 12 = 72 ft.

So, the robot has painted 72 inches of the fence before Kiteretsuki returns.