If (a_7=49) and (a=13), what is (d)?
Answer and explanation
Correct answer: 6
In an arithmetic progression, the nth term is \(a_n=a+(n-1)d\). Therefore, \(a_7=a+6d\). Substituting the given values gives \(49=13+6d\), so \(36=6d\) and \(d=6\). If 5 were chosen, the seventh term would be \(13+6\times5=43\), not 49. Exam tip: the coefficient of \(d\) in \(a_n\) is always \(n-1\).
Frequently asked questions
What is the correct answer to this question?
6
Why is this the correct answer?
In an arithmetic progression, the nth term is \(a_n=a+(n-1)d\). Therefore, \(a_7=a+6d\). Substituting the given values gives \(49=13+6d\), so \(36=6d\) and \(d=6\). If 5 were chosen, the seventh term would be \(13+6\times5=43\), not 49. Exam tip: the coefficient of \(d\) in \(a_n\) is always \(n-1\).
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Sequences and Progressions. Topic: Arithmetic Progression.
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