Question

In a proportion, the 1st, 2nd and 4th terms are 51, 68 and 108 respectively. Find the 3rd term.

Answer 1

Let the 3rd term be x.
Thus, 51:68::x:108
We know:
Product of extremes = Product of means
51 × 108 = 68 × x
⇒ 5508 = 68x
⇒ x = 5508 = 81
68
Hence, the third term is 81.