Question

y varies directly as x. if x = 7 then y = 21. find y when x = 6

Answer 1

We have directly proportional quantities. We have that

$\frac{y}{x}=\frac{21}{7}$

Then, to find y, when x = 6 is

$\frac{y}{x}=3\rightarrow y=3\cdot x\rightarrow y=3\cdot6\rightarrow y=18$

Then, when x = 6, the value for y = 18.