Question

The graph shows the function representing the recommended amount of mulch, in cubic yards, for circular flowerbeds based on the radius of the flowerbed in feet.



If the vertex of the function is at the point (0, 0.5), what is the recommended amount of mulch for a flowerbed with a radius of 20 feet? Round to the nearest whole number.

7 cubic yards
13 cubic yards
26 cubic yards
31 cubic yards

Answer 1

Vertex (0, 0.5) gives y = a r^2 + 0.5. From the graph a = 0.03, so for r = 20:

y = 0.5 + 0.03(20^2) = 0.5 + 0.03(400) = 0.5 + 12 = 12.5,

which rounds to 13 cubic yards.