A person is to count 4500 currency notes. Let an denote the number of notes he counts in the nth minute. If a1 = a2 = ... = a10 = 150 and a10, a11, ... are in A.P. with common difference d, then the time taken by him to count all notes is?<p></p>

A person is to count 4500 currency notes. Let an denote the number of notes he counts in the nth minute. If a1 = a2 = ... = a10 = 150 and a10, a11, ... are in A.P. with common difference d, then the time taken by him to count all notes is?

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Question:

A person is to count 4500 currency notes. Let an denote the number of notes he counts in the nth minute. If a1 = a2 = ... = a10 = 150 and a10, a11, ... are in A.P. with common difference d, then the time taken by him to count all notes is?

Solution: