Question

If y varies directly as x, and y is 180 when x is n and y is n when x is 5, what is the value of n?

Answer 1

n = 30

Explanation:

Let's write a proportion to represent this problem!

1. When `y = 180`, `x = n`. If we write the value of y on the top and x on the bottom, one side of the proportion is:

`180/n`

2. When `y = n`, `x = 5`. So the other side of the proportion would be:

`180/n = n/5`

3. Cross multiply.

`180(5) = n(n)`
`900 = n^2`

4. Take the square root of both sides to find `n`.

`sqrt(900) = sqrt(n^2)`

`30 = n`

That's your answer!

Check to make sure the proportion makes sense.

Does `180/30` equal `30/5`?