The fifth term of an arithmetic progression is 18 and its common difference is 3. Which of the following expressions represents its \(n\)th term?
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Answer and explanation
Correct answer: \(a_n=3n+3\)
For an AP, \(a_5=a+4d\). Thus, \(18=a+4\times3\) gives \(a=6\), so \(a_n=6+(n-1)3=3n+3\). In option B, the fifth term would be 21. Exam tip: find \(a\) before writing the general term.
Frequently asked questions
What is the correct answer to this question?
\(a_n=3n+3\)
Why is this the correct answer?
For an AP, \(a_5=a+4d\). Thus, \(18=a+4\times3\) gives \(a=6\), so \(a_n=6+(n-1)3=3n+3\). In option B, the fifth term would be 21. Exam tip: find \(a\) before writing the general term.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Arithmetic Progressions (AP). Topic: Finding the $n$th term of an AP.
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