Question

The 7th term of a GP is 8 times of 4th term. What will be the first term if 5th term is 48?

• A. 6
• B. 3
• C. 12
• D. 4.5

Answer 1

Answer:

B. 3

$a_7=8a_4$

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

$a_5=ar^4=48$

$a_7=8a_4$

$\frac{ar^6}{ar^3}=8$

$r^3=8\implies{r=2}$

$a_5=a(2^4)=48$

$a=48/16=3$