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?

1 Answer
Jun 25, 2017

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#?