# Thread: Math Final tomorrow

1. ## Math Final tomorrow

If y varies inversely as x and x=50 when y=2.7, find y when x=80(round the answer to the nearest tenth)

possible answers: 3.4, 0.2, 4.3 1.7

2. Originally Posted by lional
If y varies inversely as x and x=50 when y=2.7, find y when x=80(round the answer to the nearest tenth)

possible answers: 3.4, 0.2, 4.3 1.7

y varies inversely as x means:

$\displaystyle y=\frac{k}{x}$ where k is called the constant of proportionality.

Use your first bits of info to calculate k:

$\displaystyle 2.7=\frac{k}{50}$

$\displaystyle k=135$

Now on to your second set of info to find y when x=80.:

$\displaystyle y=\frac{135}{80}$

$\displaystyle y=1.6875\approx{1.7}$