गुणोत्तर श्रेणी \(2,6,18,\ldots\) में कितने पदों तक योग (242) होगा?
How many terms of the geometric progression \(2,6,18,\ldots\) have sum (242)?
Explanation opens after your attempt
B. (5)
Concept
(S_n=2\(3^n-1\)/(3-1)=3^n-1), and \(3^n-1=242\) gives (n=5). In exams simplify the sum and identify the power.
Why this answer is correct
The correct answer is B. (5). (S_n=2\(3^n-1\)/(3-1)=3^n-1), and \(3^n-1=242\) gives (n=5). In exams simplify the sum and identify the power.
Exam Tip
(S_n=2\(3^n-1\)/(3-1)=3^n-1) और \(3^n-1=242\) से (n=5) है। परीक्षा में योग को सरल करके घात पहचानें।
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