# Homework Help: Single variation math help

1. Sep 17, 2010

### you878

1. The problem statement, all variables and given/known data
s varies directly as r and inversely as t. s=10 when r=5 and t=3. What value of t will s=3 and r-4?

2. Relevant equations
Direct variation: y=kx; Indirect variation: y=k/x

3. The attempt at a solution
I tired s=kr=k/x and plugging in the given, but I could not get t in the end.

My real question is how to combine variations, meaning: because s varies directly AND inversely, how do you combine the variations?

2. Sep 17, 2010

Re: Variation

Write everything as a single variation, using only one constant $k$ rather than two separate expressions.

3. Sep 17, 2010

### you878

Re: Variation

Got it, thanks.