Question

If y varies jointly as x and z and y=60 when x= 10 and z=-3, find y when x=8 and z=15.

Answer 1

y = -240

Explanation:

If y varies jointly as x and z, then y/(xz) = k where k is the constant of proportion

60/10(-3) = 60/-30 = -2 = k

Now, y/(xz) = -2

y/8(15) = -2

y/120 = -2

y = -240