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

Sequence and Series: JEE Main 2010 Mathematics question

JEE Main 2010 · Annual, Paper 1 · Q5192

JEE Main 2010Annual, Paper 1MathematicsMediumSequence and Series179× since 2002

A person is to count 4500 currency notes. Let

{a_n}

denote the number of notes he counts in the

{n^{th}}

minute. If

{a_1}

{a_2}

= ....=

{a_{10}}

= 150 and

{a_{10}}

{a_{11}}

,.... are in an AP with common difference - 2, then the time taken by him to count all notes is