NDA 2017 Mathematics question
A person is to count 4500 notes. Let denote the number of notes he counts in the nth minute. If , and are in AP with the common difference , then the time taken by him to count all the notes is
Answer: (B)
Solution
In the first 10 minutes he counts notes, leaving 3000. From the 11th minute the counts are ; in such minutes he counts $
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