Y is directly proportional to x and inversely proportional to the square of z and y = 40 when x = 80 and z = 4, how do you find y when x = 7 and z = 16?

1 Answer
Bill K.
Jul 16, 2015

y=7/32 when x=7 and z=16

Explanation:

y being directly proportional to x and inversely proportional to the square of z means there is a constant k such that y=kx/z^2=(kx)/z^2.

Since y=40 when x=80 and z=4, it follows that 40=(80k)/4^2=5k which implies k=8.

Therefore, y=(8x)/z^2.

Hence, when x=7 and z=16, y=56/16^2=7/(2*16)=7/32.

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