JEE Main Mathematics question

MathematicsSequence and SeriesJEE Main

A person is to count currency notes. Let denote the number of notes he counts in the minute. If and are in AP with common difference , then the time taken by him to count all notes, is

Answer: (B)

Solution

In the first minutes he counts notes, leaving ; from the eleventh minute the counts form an AP with first term and common difference . Over further minutes he counts , i.e.

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Question ID VK-021446