Question

Find the fourth proportional to the numbers 5, 7, 30.

Answer 1

Let the fourth number be x

Then,

= 5: 7:: 30: x

We know that,

Product of extremes = product of means

∴ 5 × x = 7 × 30

= 5x = 210

= x = 210/5

= x = 42

Hence, x = 42