Question

The variable Z is directly proportional to X, and inversely proportional to Y. When X is 15 and Y is 9, Z has the value 5. What is the value of Z when X = 23, and Y = 14 Round to at least the thousandths place if needed.

Answer 1

Because Z is directly proportional to X and inversely proportional to Y, therefore
$Z=k \frac{X}{Y}$
where k = constant.

When X = 15 and Y = 9, Z = 5. Therefore
k(15/9) = 5
k = 5*(9/15) = 3
That is,
$Z= \frac{3X}{Y}$

When X = 23, and Y = 14, obtain
Z = (3*23)/14 = 4.9286

Answer:  Z = 4.929 (nearest thousandth)