Question

9. x is directly proportional to y. When x = 4, y = 9. Write an equation
for y in terms of x.

Answer 1

y = 2.25x

Explanation:

Given x is directly proportional to y then the equation relating them is

x = ky ← k is the constant of proportion

To find k use the condition when x = 4, y = 9 , then

4 = 9k ( divide both sides by 9 )

`(4)/(9)` = k

x =
`(4)/(9)` y ← equation of proportion

Multiply both sides by
`(9)/(4)` to clear the fraction

`(9)/(4)` x = y , then

y =
`(9)/(4)` x , or

y = 2.25x