एक थिएटर में पहली पंक्ति में (15) सीटें हैं और हर अगली पंक्ति में (4) सीटें अधिक हैं। (18) पंक्तियों में कुल कितनी सीटें होंगी?
In a theatre the first row has (15) seats and each next row has (4) more seats. How many seats are there in (18) rows?
Explanation opens after your attempt
C. (882)
Concept
The seats are \(15,19,23,\ldots\) and \(S_{18}=882\). Exam tip: you may also find the last row and use (S_n=\frac{n}{2}(a+l)).
Why this answer is correct
The correct answer is C. (882). The seats are \(15,19,23,\ldots\) and \(S_{18}=882\). Exam tip: you may also find the last row and use (S_n=\frac{n}{2}(a+l)).
Exam Tip
सीटों की संख्या \(15,19,23,\ldots\) है और \(S_{18}=882\)। परीक्षा में अंतिम पंक्ति निकालकर (S_n=\frac{n}{2}(a+l)) भी लगा सकते हैं।
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