Question

The value of y varies directly with x. If x=8 then y=80. What is the value of x when y = 120?

Answer 1

We know that y varies directly with x, this means that:

`y=kx`

If x=8 and y=80, then:

`\begin{gathered} 80=8k \\ k=(80)/(8) \\ k=10 \end{gathered}`

Hence:

`y=10x`

Now, if y=120, we have:

`\begin{gathered} 120=10x \\ x=(120)/(10) \\ x=12 \end{gathered}`

Therefore, if y=120 than x=12.