Question

Graham uses a 10 by 10 grid to model a decreasing pattern. He cuts off a section representing a percent of the current area so that the remaining area represents the next term in the pattern, rounded to nearest whole centimeter. The area after each cut is shown on the graph.

A graph shows number of cuts labeled 1 to 10 on the horizontal axis and remaining area (square centimeters) on the vertical axis. A line decreases from 0 to 10.

After each cut, what percentage of the previous area is the the remaining area?

10%
20%
80%
100%

Answer 1

80%

Each cut leaves the same fraction r of the previous area. From the first cut the area goes from 100 cm² to 80 cm², so r = 80/100 = 0.8, i.e. 80% remains after each cut.