x varies directly as y, and x = 153 when y = 9. Find x when y = 13.

Solution:

x varies directly as y ⇒ x ∝ y

This shows the direct proportion.

⇒ x = ky where k is the constant of proportionality.

x = 153 when y = 9

Substituting these values

153 = k (9)

k = 153/9 = 17

So we have to find x when y = 13

x = 17 (13)

x = 221

Therefore, x = 221 when y = 13.

x varies directly as y, and x = 153 when y = 9. Find x when y = 13.

Summary:

x varies directly as y, and x = 153 when y = 9. x = 221 when y = 13.