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# Find the sum up to 20 terms in the G.P 0.15, 0.015, 0.0015 .....

**Solution:**

The given G.P is

0.15, 0.015, 0.0015 .....

Here,

a = 0.15 and r = 0.015/0.15 = 0.1

It is known that

S_{n} = a (1 - r^{n})/(1 - r)

Therefore,

Substituting n = 20,we get

S_{20} = 0.15 (1 - (0.1)^{20})/(1 - 0.1)

S_{20} = 0.15/0.9 [(1 - (0.1)^{20})]

= 1/6 [(1 - (0.1)^{20})]

NCERT Solutions Class 11 Maths Chapter 9 Exercise 9.3 Question 7

## Find the sum up to 20 terms in the G.P 0.15, 0.015, 0.0015 .....

**Summary:**

We found out that the sum up to 20 terms in the G.P represented by 0.15, 0.015, 0.0015 can be found out by the formula S_{n} = a (1 - r^{n})/(1 - r) and the answer is 1/6 [(1 - (0.1)^{20})]

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