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If the first (4) terms of an arithmetic progression are (3,8,13,18), what is (S_4)?
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Answer and explanation
Correct answer: 42
Here, \(S_4\) denotes the sum of the first four terms. Thus, \(S_4=3+8+13+18=42\). Therefore, 42 is correct. Getting 40 usually indicates an addition error in one of the terms. Exam tip: for a few terms, add directly; alternatively, use \(S_n=\frac{n}{2}[2a+(n-1)d]\).
Frequently asked questions
What is the correct answer to this question?
42
Why is this the correct answer?
Here, \(S_4\) denotes the sum of the first four terms. Thus, \(S_4=3+8+13+18=42\). Therefore, 42 is correct. Getting 40 usually indicates an addition error in one of the terms. Exam tip: for a few terms, add directly; alternatively, use \(S_n=\frac{n}{2}[2a+(n-1)d]\).
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Sequences and Progressions. Topic: Arithmetic Progression.
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