A = 2•3.14•3•8 + 2•3.14•3^2 = 207.34512
Answer:
Option A. 65 trees
Step-by-step explanation:
From the question given:
50 trees was in the forest. Then 23 of them were cut down.
The remaining trees = 50 — 23 = 27 trees.
Now 38 new trees were plant.
Total trees after cutting and planting = 27 + 38 = 65 trees
Total cost, C = 8x^2 + 12xz
volume, V = (x^2)*z = 10
C = 8x^2 + 12x*10/x^2
= 8x^2 + 120/x
dC/dx = 16x - 120/x^2 = 0
16x = 120/x^2
x^3 = 120/16
x = 1.957 ft
d^2C/dx^2 = 16 +240/x^3 = +ve for x = 1.957
so, C is minimum when
x = 1.957 ft z = 2.61 ft
Length of the base x is 1.957 ft and height of side z is 2.61 ft
