Question

Find the fourth proportional to 12, 18 and 20.
12, 18 और 20 का चौथा आनुपातिक ज्ञात करें।
(a) 30
(b) 50
(c) 35
(d) 40​

Answer 1

12 : 18 : : 20 : x

product of means ≈ product of extremes

18 × 20 ≈ 12 × x

360 = 12x

12 x = 360

x = 360/12

x = 30

Hence, option a ). 30 is correct.