Browse · MATH
Printjmc
geometry junior
Problem
In the staircase-shaped region below, all angles that look like right angles are right angles, and each of the eight congruent sides marked with a tick mark have length 1 foot. If the region has area 53 square feet, what is the number of feet in the perimeter of the region? 
Solution
We can look at the region as a rectangle with a smaller staircase-shaped region removed from its upper-right corner. We extend two of its sides to complete the rectangle: Dissecting the small staircase, we see it consists of ten 1 ft by 1 ft squares and thus has area 10 square feet. Let the height of the rectangle have length feet, so the area of the rectangle is square feet. Thus we can write the area of the staircase-shaped region as . Setting this equal to and solving for yields feet.
Finally, the perimeter of the region is feet. (Notice how this is equal to the perimeter of the rectangle -- if we shift each horizontal side with length 1 upwards and each vertical side with length 1 rightwards, we get a rectangle.)
Finally, the perimeter of the region is feet. (Notice how this is equal to the perimeter of the rectangle -- if we shift each horizontal side with length 1 upwards and each vertical side with length 1 rightwards, we get a rectangle.)
Final answer
32