Question

Find the fourth proportional to the following:

1.5, 4.5, 3.5

Answer 1

Let x be the fourth proportional

1.5 : 4.5 = 3.5 : x

⇒ `1.5/4.5 = 3.5/x`

⇒ 1.5x = 4.5 × 3.5

⇒ 1.5x = 15.75

⇒ x = `15.75/1.5`

⇒ x = 10.5

The fourth proportional is 10.5.