Question

y varies jointly with p and q. When p = 5 and q = 2, y = 80. Find y when p = 4 and q = 5.

a. y = 20

b. y = 120

c. y = 160

d. y = 240

Answer 1

if y varies jointly with p and q then this implies:\[y=kpq\]where k is some constant.
use the given values of p=5, q=2 and y=80 to find k.
then use the resulting equation to solve for y.

Answer 2

how do i find k?

Answer 3

you are told that: p=5, q=2 and y=80 - use these values

Answer 4

80 = k10
k = 8

Answer 5

perfect!

Answer 6

so now you know:\[y=8pq\]

Answer 7

Find y when p = 4 and q = 5.

Answer 8

y = (8)(4)(5)
y = 160

Answer 9

great! well done! :)

Answer 10

thank you very much!

Answer 11

yw :)