Question

Please help, I don't understand.
If y varies directly as x, and y is 400 when x is r and y is r when x is 4, what is the numeric constant of variation in this relation?

Answer 1

\[y=kx\] you need \(k\)
you are given
\[400=kr\] and \[r=4k\]

Answer 2

that makes \(400=4k^2\) and so \(100=k^2\) making \(k=10\)

Answer 3

Thanks so much. NOW i understand