Question

W varies directly as r cubed and inversely as s. If w=24 when r= 4 and s= 8, find out when w= 81 and s= 27?

Answer 1

Translating the word problem into a symbolic statement: W = kr³/s. Find k by letting W = 24, r = 4 and s = 8:

k·4³

24 = --------

8

This reduces to 3 = 4^3*k, or 3 = 64k, or k = 3/64 (the constant of proportionality).

3r^3

w = ---------

64