Question

y varies inversely with x. If y=40 when x=16, find x when y=-5.

Answer 1

Inverse variation is:

\(y = \dfrac{k}{x}\)

Plug in what we know:

\(40 = \dfrac{k}{16}\)

Now multiply 16 to both sides, what's 40 * 16?

Answer 2

Can you multiply 40 * 16? @INarcolepsy

Answer 3

640

Answer 4

Yes, so the constant is 640.

Plug in -5 for 'y' and 640 for 'k':

\(y = \dfrac{k}{x}\)

\(-5 = \dfrac{640}{x}\)

Multiply 'x' to both sides;

\(-5x = 640\)

Divide -5 to both sides, what's 640 / -5?

Answer 5

128

Answer 6

Yes, that's our answer @INarcolepsy