Question

For a G.P if a=5 and r=3/5 then find S4​

Answer 1

Step-by-step explanation:

a = 5 r = 3/5

S4 = a(r)^4 - 1/ r -1

$= 5 { (\frac{3}{5}) }^{4 - 1} \div \frac{3}{5} - 1 \\ = \frac{5 \times \frac{ {3}^{3} }{ {5}^{3} } }{ \frac{3}{5} - 1} \\ = \frac{ \frac{27}{25} }{ \frac{3 - 5}{5} } \\ = \frac{27}{25} \times - \frac{5}{2} \\ = - \frac{ 27}{10}$

hope you get your answer