Question

If x is directly proportional to y and x= -12 when y= 3, what is the value of x when y = -4?

Answer 1

x = 16

Explanation:

given x is directly proportional to y, then the equation relating them is

x = ky ← k is the constant of proportionality

to find k , substitute x = - 12 when y = 3 into the equation

- 12 = 3k ( divide both sides by 3 )

- 4 = k

x = - 4y ← equation of proportion

when y = - 4 , then

x = - 4 × - 4 = 16