The first (5) terms of an AP are (3,7,11,15,19). What is their sum?
Answer and explanation
Correct answer: 55
The sum of the five given terms is 3 + 7 + 11 + 15 + 19 = 55. Hence, the correct answer is 55. It can also be checked using the AP sum formula: \(S_5=\frac{5}{2}[2(3)+4(4)]=55\). Although 57 is close, it is not the sum of the given terms. Exam tip: for a small number of terms, direct addition is a quick way to verify the answer.
Frequently asked questions
What is the correct answer to this question?
55
Why is this the correct answer?
The sum of the five given terms is 3 + 7 + 11 + 15 + 19 = 55. Hence, the correct answer is 55. It can also be checked using the AP sum formula: \(S_5=\frac{5}{2}[2(3)+4(4)]=55\). Although 57 is close, it is not the sum of the given terms. Exam tip: for a small number of terms, direct addition is a quick way to verify the answer.
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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