A student reads (55) pages in the first month and (25) pages more each next month. In which month will the student read (355) pages?

Correct answer: 13

This forms an arithmetic progression with first term \(a=55\) and common difference \(d=25\). Pages read in the \(n\)th month are \(a_n=55+(n-1)25\). Setting this equal to 355 gives \(55+(n-1)25=355\), so \(25(n-1)=300\), \(n-1=12\), and \(n=13\). Hence, the student reads 355 pages in the 13th month. In the 12th month, the student would read only \(330\) pages. Exam tip: use \(a_n=a+(n-1)d\) when the quantity for a particular term is given.