# Direct & Joint Proportions

• Oct 14th 2011, 06:18 PM
gellie
Direct & Joint Proportions

If n is directly proportional to the cube of m and that n = 27 when m = 1 1/2, find:
a) the value of n when m = 2
d) the value of m when n = 125
• Oct 14th 2011, 09:26 PM
mr fantastic
Re: Direct & Joint Proportions
Quote:

Originally Posted by gellie

If n is directly proportional to the cube of m and that n = 27 when m = 1 1/2, find:
a) the value of n when m = 2
d) the value of m when n = 125

$n \propto m^3 \Rightarrow n = km^3$.

Use n = 27 when m = 1 1/2 to get the value of k. Then use your formula to answer a) and d).

If you need more help, please show all your work and say where you're stuck.