Y varies inversely as x. y is 4 when x is 16. How do you find y if x is 20?

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Answer 1 · 2016-10-18T11:37:15

#y=16/5#

If y varies inversely with x, then y is inversely proportional to x.
# yprop1/x#

Another way to write this is #y=k/x# where #k# is a proportionality constant.

First, find #k# using this equation.

#y=k/x" "# which gives #k = xy#

#k = 16xx4color(white)(aaa)#Subsitute #4# for #y# and #16# for #x#.

#k = 64#

To find #y# when #x=20#:

plug #k=64# and #x=20# back into the original equation.

#y=k/x#

#y=64/20#

#y=16/5#