Question

Assume r varies jointly with x and y. If r=15 when x=3 and y=4. Find r when x=16 and y =1.25

What is r when x=16 and y=1.25

Answer 1

see explanation

Explanation:

given that r varies jointly with x and y then the equation relating them is

r = kxy ← k is the constant of variation

To find k use the condition r = 15 when x = 3 and y = 4

k =
`(r)/(xy)` =
`(15)/(12)` = 1.25

r = 1.25xy ← equation of variation

When x = 16 and y = 1.25, then

r = 1.25 × 16 × 1.25 = 25