Question

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

Answer 1

"y varies jointly with p and q"

means that

y = kpq

for some (not known yet) constant k

Answer 2

"When p = 5 and q = 2, y = 80"

this means that

y = kpq

becomes

80 = k*5*2

which turns into

80 = 10k

Answer 3

Solve that for k and tell me what you get

Answer 4

8?

Answer 5

yes good

Answer 6

So

y = kpq

turns into

y = 8pq

Answer 7

so its 8*4*5

Answer 8

Last part:

Find y when p = 4 and q = 5

Plug in p = 4 and q = 5 to go from

y = 8pq

to

y = 8*4*5

y = ??

Answer 9

yes

Answer 10

thank you

Answer 11

you're welcoem

Answer 12

welcome*