Question

Select the correct answer. Which expression represents the series 1 + 5 + 25 + 125 + 625 ? A. B. C. D.

Answer 1

Answer:

Sum of the question is 781.

Answer 2

1+ 5 + 25 + 125 + 625 = 781

Step-by-step explanation:

Given series 1+ 5 + 25 + 125 + 625

First term(a) = 1

second term = 5

Third term = 25 and so on ......

It is a g.p series.

common ratio(r) = $\frac{second\ term }{first \ term}$= $\frac {5}{1}$ = 5

$s_n = \frac{a(r^n-1)}{(r-1)}$

⇔$s_n = \frac{1(5^5-1)}{(5-1)}$           [ n= 5, a = 1 and r = 5]

⇔$s_n = \frac{1(3125-1)}{(4)}$

⇔$s_n = 781$