Home › IBPS RRB › Reasoning › series_coding_relations › The sum 7 + 77 + 777 + ... to n terms is found by:
The sum 7 + 77 + 777 + ... to n terms is found by:
AAdding the terms directly
BTreating it as an A.P.
CGuessing the total
DRelating it to a G.P.
Answer & Solution
Correct answer: D. Relating it to a G.P.
1. The terms have no constant ratio themselves.
2. Each can be rewritten with powers of ten.
3. That turns the problem into a G.P.
_Source: NCERT Class 11 Mathematics, Chapter 8, Sequences and Series._
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