Suppose a is directly proportional to b, but inversely proportional to c. If a = 2 when b = 5 and c = 9, then what is c when b = 3?

Guest Apr 5, 2019

#2**+1 **

No offence but you're really not helpful. I understand that any help I get at all is completly out of good will but still. The question is what is c WHEN B EQAULS 3.

Guest Apr 5, 2019

#5**+3 **

Suppose a is directly proportional to b, but inversely proportional to c. If a = 2 when b = 5 and c = 9, then what is c when b = 3?

\(a=kb\qquad \text{where k is a constant}\\ \text{When a=2, b=5 so}\\ 2=k*5\\ k=\frac{2}{5}=0.4\\ so\\ a=0.4b\)

\(a=\frac{m}{c}\qquad \text{where m is a constant}\\ \text{when a=2, c=9 }\\ 2=\frac{m}{9}\\ m=18\\ so\\ a=\frac{18}{c}\\ \text{sub in 0.4b for a}\\ 0.4b=\frac{18}{c}\\ when\; b=3\\ 0.4*3=\frac{18}{c}\\ 1.2=\frac{18}{c}\\ c=\frac{18}{1.2}\\ c=15 \)

When b=3 c=15

You need to check for careless errors :)

Melody Apr 5, 2019