The value of y varies directly with x, and y=28 when x=7. Find y when x=4 by first finding k.

Direct proportionality is the type of proportionality where an increase in one quantity or variable causes a corresponding increase in another quantity.

Therefore; y varies directly as x

Hence; y α x

y = k x where k is a constant

if y = 28 and x = 7, then k = 28/4 = 4

hence, y = 4 k

when x = 4, then y = 16