What will be the (13)th term of the AP (120,109,98,\ldots)?
Answer and explanation
Correct answer: -12
Here, the first term is \(a=120\) and the common difference is \(d=109-120=-11\). The \(n\)th term is given by \(a_n=a+(n-1)d\). Thus, \(a_{13}=120+(13-1)(-11)=120-132=-12\). Therefore, \(-12\) is correct. \(-10\) can result from incorrectly counting the number of differences or using \(n\) instead of \((n-1)\). Exam tip: for the \(n\)th term, always use \((n-1)\) common differences.
Frequently asked questions
What is the correct answer to this question?
-12
Why is this the correct answer?
Here, the first term is \(a=120\) and the common difference is \(d=109-120=-11\). The \(n\)th term is given by \(a_n=a+(n-1)d\). Thus, \(a_{13}=120+(13-1)(-11)=120-132=-12\). Therefore, \(-12\) is correct. \(-10\) can result from incorrectly counting the number of differences or using \(n\) instead of \((n-1)\). Exam tip: for the \(n\)th term, always use \((n-1)\) common differences.
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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