What is the (11)th term in the AP (9,6,3,0,\ldots)?
Answer and explanation
Correct answer: \(-21\)
In this AP, the first term is \(a=9\) and the common difference is \(d=6-9=-3\). Using \(a_n=a+(n-1)d\), we get \(a_{11}=9+(11-1)(-3)=9-30=-21\). \(-18\) is the 10th term, so it is a close but incorrect option. Exam tip: always use \(n-1\), not \(n\), in the nth-term formula.
Frequently asked questions
What is the correct answer to this question?
\(-21\)
Why is this the correct answer?
In this AP, the first term is \(a=9\) and the common difference is \(d=6-9=-3\). Using \(a_n=a+(n-1)d\), we get \(a_{11}=9+(11-1)(-3)=9-30=-21\). \(-18\) is the 10th term, so it is a close but incorrect option. 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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