If \(a_n=\frac{n(n+5)}{3}\), what is the value of \(a_6\)?
Answer and explanation
Correct answer: 22
Putting \(n=6\) into the formula gives \(a_6=\frac{6(6+5)}{3}=\frac{6\times11}{3}=22\). Therefore, 22 is correct. The close distractor 24 can result from an arithmetic error while adding \(6+5\) or simplifying the division. Exam tip: to find \(a_n\), substitute the value of \(n\) carefully before simplifying multiplication and division.
Frequently asked questions
What is the correct answer to this question?
22
Why is this the correct answer?
Putting \(n=6\) into the formula gives \(a_6=\frac{6(6+5)}{3}=\frac{6\times11}{3}=22\). Therefore, 22 is correct. The close distractor 24 can result from an arithmetic error while adding \(6+5\) or simplifying the division. Exam tip: to find \(a_n\), substitute the value of \(n\) carefully before simplifying multiplication and division.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Sequences and Progressions. Topic: nth term.
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