Mathematics - Sequence & Series Question with Solution | TestHub

A person is to count 4500 currency notes. Let $a_n$ denote the number of notes he counts in the ${\mathrm{n}}^{\text{th }}$ minute. If ${\mathrm{a}}_1={\mathrm{a}}_2=\dots \dots ={\mathrm{a}}_{10}=150$ and ${\mathrm{a}}_{10},{\mathrm{a}}_{11},\dots \dots$ are in A.P. with common difference $-2$, then the time taken by him to count all notes is