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Which term of the AP (15,21,27,\ldots) is (111)?

Answer and explanation

Correct answer: 17th term

Here, the first term is \(a=15\) and the common difference is \(d=21-15=6\). The \(n\)th term is \(a_n=a+(n-1)d\). Thus, \(111=15+(n-1)\times6\), so \(96=6(n-1)\) and \(n=17\). Therefore, 111 is the 17th term. The 16th term is \(105\), so it is close but not correct. Exam tip: while finding a term number, remember that the formula contains \((n-1)\).

Related tags

Arithmetic ProgressionNth TermTerm NumberCommon DifferenceClass 10 MathematicsFinding The $N$Th Term Of An ApFinding The N Th Term Of An ApArithmetic Progressions (Ap)

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