Question

Find the fourth proportional to the following:

`1/2, 1/3, 1/4`

Answer 1

Let x be the fourth proportional

`1/2 : 1/3 = 1/4 : x`

⇒ `(1/2)/(1/3) = (1/4)/x`

⇒ `3/2 = 1/(4x)`

⇒ 3 × 4x = 2 × 1

⇒ 12x = 2

⇒ x = `2/12`

⇒ x = `1/6`

The fourth proportional is `1/6`.