If (a=3) and (d=9), what is the (7)th term?
Answer and explanation
Correct answer: 57
The nth term of an AP is \(a_n=a+(n-1)d\). Here, \(a=3\), \(d=9\), and \(n=7\). Thus, \(a_7=3+(7-1)\times9=3+54=57\). Therefore, 57 is correct. The value 54 is only \(6d\); the first term 3 has not been added to it. Exam tip: Always use \(n-1\), not \(n\), in the nth-term formula.
Frequently asked questions
What is the correct answer to this question?
57
Why is this the correct answer?
The nth term of an AP is \(a_n=a+(n-1)d\). Here, \(a=3\), \(d=9\), and \(n=7\). Thus, \(a_7=3+(7-1)\times9=3+54=57\). Therefore, 57 is correct. The value 54 is only \(6d\); the first term 3 has not been added to it. Exam tip: Always use \(n-1\), not \(n\), in the nth-term formula.
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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