Question

Suppose that y varies jointly with w and x and inversely with z and y = 400 when w = 10, x = 25, and z = 5. Write the equation that models the relationship.

Answer 1

Well...Jointly (directly) with w and x and inversely with z...

\[\large y = \frac{kwx}{z}\]

When y = 400 x = 25 w = 10 and z = 5 we have

\[\large 2000 = k(25)(10)\]

\[\large 2000 = k(250)\]

\[\large k = 8\]

Now we know the general formula for this will be

\[\large y = \frac{8wx}{z}\]