36 Views

the sum of first 20 terms of sequence 0.7,0.77,-- is


Divya 28th Jun, 2020
Answer (1)
Shivang Dubey 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

Related Questions

UEI Global, Hotel Management ...
Apply
Training & Placement Guarantee | Top Recruiters: The Oberoi, Taj, Lee Meridien, Hyatt and many more
VIT Bhopal University | M.Tec...
Apply
M.Tech admissions open @ VIT Bhopal University | Highest CTC 52 LPA | Apply now
Amity University | M.Tech Adm...
Apply
Ranked amongst top 3% universities globally (QS Rankings).
Amity University Noida MBA Ad...
Apply
Amongst top 3% universities globally (QS Rankings)
Graphic Era (Deemed to be Uni...
Apply
NAAC A+ Grade | Among top 100 universities of India (NIRF 2024) | 40 crore+ scholarships distributed
XAT- Xavier Aptitude Test 2026
Apply
75+ years of legacy | #1 Entrance Exam | Score accepted by 250+ BSchools | Apply now
View All Application Forms

Download the Careers360 App on your Android phone

Regular exam updates, QnA, Predictors, College Applications & E-books now on your Mobile

150M+ Students
30,000+ Colleges
500+ Exams
1500+ E-books