What is the (n)th term of the sequence (15,30,45,60,\ldots)?
Answer and explanation
Correct answer: \(a_n=15n\)
This is an arithmetic progression with first term \(a=15\) and common difference \(d=15\). Thus, \(a_n=a+(n-1)d=15+(n-1)15=15n\). In option B, putting \(n=1\) gives the first term as 0, so it is incorrect. Exam tip: Substitute \(n=1\) in a proposed rule to check whether it gives the first term.
Frequently asked questions
What is the correct answer to this question?
\(a_n=15n\)
Why is this the correct answer?
This is an arithmetic progression with first term \(a=15\) and common difference \(d=15\). Thus, \(a_n=a+(n-1)d=15+(n-1)15=15n\). In option B, putting \(n=1\) gives the first term as 0, so it is incorrect. Exam tip: Substitute \(n=1\) in a proposed rule to check whether it gives the first term.
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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