Use app×
Join Bloom Tuition
One on One Online Tuition
JEE MAIN 2025 Foundation Course
NEET 2025 Foundation Course
CLASS 12 FOUNDATION COURSE
CLASS 10 FOUNDATION COURSE
CLASS 9 FOUNDATION COURSE
CLASS 8 FOUNDATION COURSE
0 votes
1.0k views
in Arithmetic Progression by (350 points)
closed by

If sum of n terms of an AP is 5n2-3n, then sum of its 100th term is 

1 Answer

+2 votes
by (44.0k points)
selected by
 
Best answer

\(\sum_{i=1}^n \) ai = 5n2 - 3n

= 5n2 + 5n - 8n

= 10\(\big(\frac{n^2+n}{2}\big)\)- 8n

=10 \(\sum_{i=1}^n \) i - 8 \(\sum_{i=1}^n \)1

\(\sum_{i=1}^n \)(10 i -8)

ith term of sequence = 10i - 8

100th term of sequence = 1000-8 = 992

Sum of digits = 9 + 9 + 2 = 20

Welcome to Sarthaks eConnect: A unique platform where students can interact with teachers/experts/students to get solutions to their queries. Students (upto class 10+2) preparing for All Government Exams, CBSE Board Exam, ICSE Board Exam, State Board Exam, JEE (Mains+Advance) and NEET can ask questions from any subject and get quick answers by subject teachers/ experts/mentors/students.

...