If y varies inversely with x, and y = 5 when x = 7, what is the value of y when x = 4?

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Answer 1 · 2016-07-07T13:35:48

#y = 8 3/4# when #x = 4#

An inverse variation: #y = k/x#

We are given #y# and #x#. We need to solve for #k# so we can find #y# when #x# equals #4#.

#5 = k/7#

#7/1 * 5 = k/cancel7 * cancel7/1#

#35 = k#

We found what #k# is, so know we can make our inverse variation equation.

#y = 35/x#

Now let's plug in #4# for #x# to find #y#.

#y = 35/4#

#y = 8 3/4#