The sum of 3 terms of a G.P. is 21/4 and their product is 1, then the

1.	The sum of 3 terms of a G.P. is 21/4 and their product is 1, then the common ratio is(A) 1(B) 2(C) 4(D) 8
Answer» Correct option is (C) 4 Let three terms be \(\frac{a}r, a,ar\) According to the given conditions, \(\frac{a}r+a+ar=21/4\).......(i) and \(\frac{a}r\) x a x ar = 1, i.e., a³ = 1 ∴ a = 1 ∴ from equation (i), we get \(\frac1r+1+r=21/4\) By solving this, we get r = 4.

The sum of 3 terms of a G.P. is 21/4 and their product is 1, then the common ratio is(A) 1(B) 2(C) 4(D) 8

Answer»

Correct option is (C) 4

Let three terms be \(\frac{a}r, a,ar\)

According to the given conditions,

\(\frac{a}r+a+ar=21/4\).......(i)

and \(\frac{a}r\) x a x ar = 1,

i.e., a³ = 1

∴ a = 1

∴ from equation (i), we get

\(\frac1r+1+r=21/4\)

By solving this, we get r = 4.