Question

If P is directly proportional to Q. And Q = 30 when P = 40. Find Q when P = 70

Answer 1

Q = 52.5

Explanation:

given P is directly proportional to Q then the equation relating them is

P = kQ ← k is the constant of proportion

to find k use the condition Q = 30 when P = 40 , then

40 = 30k ( divide both sides by 30 )

`(40)/(30)` =
`(4)/(3)` = k

P =
`(4)/(3)` Q ← equation of proportion

when P = 70 , then

70 =
`(4)/(3)` Q ( multiply both sides by 3 to clear the fraction )

210 = 4Q ( divide both sides by 4 )

52.5 = Q