The original volume equation looks like this: V = 1/3 * h * (x^2)
After the side is reduced by 0.002, the new volume would look like V1 = 1/3 * h
* (x-0.002) ^ 2
Then we have:
V-V1 = 1/3*h*(x^2) - 1/3*h*(x – 0.002) ^2
= 1/3 * h *(x^2 - (x – 0.002) ^2)
= 1/3 * h * (0.004x - 0.00004)
The rate of decreasing is computed by:
(V-V1)/V * 100% = [1/3 * h *(0.004x - 0.00004)] / [1/3 * h * (x ^ 2)] *
100% this would be equal to (0.004x - 0.00004) / (x^2) * 100%
So replace x by 200, you’ll get:
(0.004(200) - 0.00004) / (200^2) * 100%
= 0.001999% is the rate of decreasing.