Question

If y varies directly with x and y=36
when x=6
, find the value of y when x=4

Answer 1

y=6x, and y(4) = 24

Explanation:

y = kx "y varies directly with x," where k tells us by how much.

We can find k with the information ". . .and y=36

when x=6."

y = kx

36 = k6 for (5,36)

k = 36/6

k = 6

The equation is y = 6x

When x=4, y = 6*4;

y = 24 when x = 4

Answer 2

y = 24

Explanation:

given y varies directly with x then the equation relating them is

y = kx ← k is the constant of variation

to find k, substitute y = 36, x = 6 into the equation

36 = 6k ( divide both sides by 6 )

6 = k

y = 6x ← equation of variation

when x = 4, substitute into equation

y = 6x = 6 × 4 = 24