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Riya saves money daily for 12 days. She saves ₹50 on the first day and ₹10 more on each successive day. She claims that her total saving is ₹2520. Which of the following analyses is correct?

Answer and explanation

Correct answer: She multiplied by \(n\) instead of \(n/2\); the correct sum is ₹1260.

The 12th-day saving is \(50+11\times10=160\). Hence, the sum is \(\frac{12}{2}(50+160)=1260\). Riya used \(n\) instead of \(n/2\). Exam tip: find the last term before applying the sum formula.

Related tags

Arithmetic ProgressionSum Of ApNth TermError AnalysisClass 10 MathematicsFinding The Sum Of The First $N$ Terms Of An ApFinding The Sum Of The First N Terms Of An ApArithmetic Progressions (Ap)

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