A person is to count 4500 notes. Let aₙ denote the number of notes he counts in the nth minute. If a₁ = a₂ = … = a₁₀ = 150, and a₁₀, a₁₁, a₁₂ … are in AP with the common difference -2, then the time taken by him to count all the notes is

Mathematics 2017 NDA Mathematics 2017 NDA 2017

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