Question

The variable Z is directly proportional to X, and inversely proportional to Y. When X is 10 and Y is 4, Z has the value 47.5.

What is the value of Z when X = 13, and Y = 10

Answer 1

Because Z is directly proportional to X and inversely proportional to Y, therefore

`Z=k( (X)/(Y)),\\k=constant`

When X=10 and Y=4, Z=47.5.
Therefore
k(10/4) = 47.5
2.5k = 47.5
k = 19.

That is,

`Z= (19X)/(Y)`

When X=13 and Y=10, obtain
Z = (19*13)/10 = 24.7

Answer: 24.7