Question

Let a, b, c form a G.P. of common ratio r, with 0 < r < 1.

If a, 2b, 3c form an A.P., then r equals –

• A. ½
• B. 1/3
• C. 2/3
• D. None of these

Answer 1

Answer: (B)

1/3

Answer 2

Let a =a, b = ar, c = ar² Now, 4b = a + 3c

4ar = a + 3ar² Ž 3r² – 4r + 1 = 0

Ž r = 1, 1/3 (But 0 < r < 1) \ r = 1/3