What is the sum of the first (25) terms of the AP (14,18,22,\ldots)?
Answer and explanation
Correct answer: 1550
Here, the first term is \(a=14\), the common difference is \(d=18-14=4\), and the number of terms is \(n=25\). The 25th term is \(a_{25}=a+(n-1)d=14+24\times4=110\). Hence, \(S_{25}=\frac{n}{2}(a+l)=\frac{25}{2}(14+110)=1550\). Therefore, 1550 is the correct answer. A close option such as 1575 may result from an error in finding the last term or the number of terms. Exam tip: always check the \(n-1\) factor while finding the last term.
Frequently asked questions
What is the correct answer to this question?
1550
Why is this the correct answer?
Here, the first term is \(a=14\), the common difference is \(d=18-14=4\), and the number of terms is \(n=25\). The 25th term is \(a_{25}=a+(n-1)d=14+24\times4=110\). Hence, \(S_{25}=\frac{n}{2}(a+l)=\frac{25}{2}(14+110)=1550\). Therefore, 1550 is the correct answer. A close option such as 1575 may result from an error in finding the last term or the number of terms. Exam tip: always check the \(n-1\) factor while finding the last term.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Arithmetic Progressions (AP). Topic: Finding the sum of the first $n$ terms of an AP.
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