Find the (15)th term of the AP (40,36,32,28,\ldots).
Answer and explanation
Correct answer: \(-16\)
For this AP, the first term is \(a=40\) and the common difference is \(d=36-40=-4\). The \(n\)th term is \(a_n=a+(n-1)d\). Therefore, \(a_{15}=40+(15-1)(-4)=40-56=-16\). Hence, option \(\text{C}\) is correct. \(-20\) would be obtained for the 16th term, not the 15th term. Exam tip: for the \(n\)th term, use the common difference \((n-1)\) times.
Frequently asked questions
What is the correct answer to this question?
\(-16\)
Why is this the correct answer?
For this AP, the first term is \(a=40\) and the common difference is \(d=36-40=-4\). The \(n\)th term is \(a_n=a+(n-1)d\). Therefore, \(a_{15}=40+(15-1)(-4)=40-56=-16\). Hence, option \(\text{C}\) is correct. \(-20\) would be obtained for the 16th term, not the 15th term. Exam tip: for the \(n\)th term, use the common difference \((n-1)\) times.
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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