the sum of first 20 terms of sequence 0.7,0.77,-- is
Answer (1)
28th Jun, 2020
Hey Divya
Solution (S):
S = 0.7+0.77+0.777+....0.7777
=7(0.1+0.11+0.11+0.111+.......+0.1111....)
= 79[0.9+0.99+0.99+0.999+...........)
=79[(1−0.1)+(1−0.01)+....+(1−0.000......1)]
=7/9 * [20 − (1 / 10+1 / 10^2+......1 / 20^20)]
Therefore, a= r = 1/10
=7/ 9* [20−1/9 * (1−10^−20)
=7 / 81 * [179 + 10^−20] -> Answer
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