Question

Let A1, A2, A3, … be an increasing geometric progression of positive real numbers. If A1A3A5A7 = $\frac {1}{1296}$ and A2 + A4 = $\frac {7}{36}$ then, the value of A6 + A8 + A10 is equal to

• A. 33
• B. 37
• C. 43
• D. 47

Answer 1

Answer: (C)

43

Answer 2

$\frac {A_4}{r^3}. \frac {A_4}{r} . A_4r . A_4r^3 = \frac {1}{1296}$

$A_4 = \frac 16$

$A_2 = \frac {7}{36} - \frac 16$

$A_2= \frac {1}{36}$
So, $A_6 + A_8 + A_{10} = 1 + 6 + 36$
$= 43$

So, the correct option is (C): $43$