Question

Find the number of terms in the GP :3,9,27, ...........,531441

• A. 10
• B. 13
• C. 12
• D. 15

Answer 1

Answer:

C. 12

$a=3,r=9/3=3, a_n=531441$

$a_n=ar^{(n-1)}$

$531441=3\times3^{(n-1)}$

$3^{(n-1)}=531441/3=177174$

$177174=3^{11}=3^{(n-1)}$

$n-1=11$

$n=12$