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?

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Answer 1 · 2017-06-25T20:08:04

n = 30

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 $30/5$ ?