Answer:
1 inches per cube
As required.
Step-by-step explanation:
Solution:
Given:
Volume = l3
dV / dt = 3 l2dl / dt
dv / dt = 0.5 inches cubed / hour
Surface area = 6 l2
Differentiate with respect to t: s = 6 l2
We get:
ds / dt = 12 l dl / dt
and dv / dt = = 0.5 inches cubed / hour
we know that:
dv / dt = 20 = 3 l2dl / dt
0.5 = 3 l2 (dl / dv)(dv / dt)
0.5 = 3l2 dl / dt
0.5 / 3l2 = dl / dt
Put 0.5 / 3l2 = dl / dt in eq ds / dt = 12 l dl / dt
ds / dt = 12 l (0.5 / 3l2)
= 4(0.5) / l
= 2 / 2 inches pr cube [ l = 2 inches per cube]
= 1 inches per cube
As required.
