Answer:
see explanation
Step-by-step 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 = =
= 1.25
r = 1.25xy ← equation of variation
When x = 16 and y = 1.25, then
r = 1.25 × 16 × 1.25 = 25