Assume that all variables represent positive numbers. Assume that $r$ varies directly with $s$ . If $r = 10$ when $s = 4$ , find $s$ when $S = 12$ .
A) $r = 29$
B) $r = 28$
C) $r = 27$
D) $r = 30$
E) $r = 26$

Question

Quizplus · Accepted Answer

We can use the formula for direct variation, which is $r = ks$ where $k$ is the constant of variation. To find $k$, we can use the given data: when $r=10$ and $s=4$, we have $$10=k\cdot4.$$ Solving for $k$, we get $k=2.5$. Now we can use this constant to solve for $r$ when $s=12$: $$r=2.5\cdot12 = 30.$$ Therefore, the answer is D.

Assume That All Variables Represent Positive Numbers rrr Varies Directly With sss

Assume That All Variables Represent Positive Numbers $r$ Varies Directly With $s$