The 12th term of a G.P. whose first term is 1/8 and second term is 1/2 is
The 12th term of a G.P. whose first term is 1/8 and second term is 1/2 is
A) 411
B) 2 × 411
C) 2 × 49
D) 2 × 410
4 views
2 Answers
Correct option is (C) \(2 \times 4^{9}\)
\(a_1=\frac18,a_2=\frac12\)
\(\therefore r=\frac{a_2}{a_1}=\cfrac{\frac{1}{2}}{\frac{1}{8}}\)
\(=\frac{1}{2}\times8=4\)
\(\therefore\) \(12^{th}\) term in G.P. \(=a_{12}=ar^{11}\)
\(=\frac18\times4^{11}\)
\(=\frac{4\times4\times4^9}8\)
\(=2\times4^9\)
Hence, \(12^{th}\) term of G.P. is \(2 \times 4^{9}.\)
4 views
Answered