What is the (31)st term of the AP (-4,1,6,\ldots)?
Answer and explanation
Correct answer: 146
The first term of the AP is \(a=-4\), and its common difference is \(d=1-(-4)=5\). The \(n\)th term is given by \(a_n=a+(n-1)d\). Therefore, \(a_{31}=-4+(31-1)\times5=-4+150=146\). Hence, 146 is the correct answer. Using \(31\times5\) instead of \((31-1)\times5\) would give 151, which is incorrect. Exam tip: always use \(n-1\) in the formula for the \(n\)th term.
Frequently asked questions
What is the correct answer to this question?
146
Why is this the correct answer?
The first term of the AP is \(a=-4\), and its common difference is \(d=1-(-4)=5\). The \(n\)th term is given by \(a_n=a+(n-1)d\). Therefore, \(a_{31}=-4+(31-1)\times5=-4+150=146\). Hence, 146 is the correct answer. Using \(31\times5\) instead of \((31-1)\times5\) would give 151, which is incorrect. Exam tip: always use \(n-1\) in the formula for the \(n\)th term.
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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