In a school, the first class has (30) students and each next class has (5) more students. How many students are there in (6) classes?
Answer and explanation
Correct answer: 255
The numbers of students form an AP: 30, 35, 40, 45, 50, 55. Here, \(a=30\), \(d=5\), and \(n=6\). Therefore, \(S_6=\frac{6}{2}[2(30)+(6-1)5]=3(85)=255\). Hence, 255 is the correct answer. 260 can result from incorrectly adding the final class size. Exam tip: identify \(a\), \(d\), and \(n\) before applying the AP sum formula.
Frequently asked questions
What is the correct answer to this question?
255
Why is this the correct answer?
The numbers of students form an AP: 30, 35, 40, 45, 50, 55. Here, \(a=30\), \(d=5\), and \(n=6\). Therefore, \(S_6=\frac{6}{2}[2(30)+(6-1)5]=3(85)=255\). Hence, 255 is the correct answer. 260 can result from incorrectly adding the final class size. Exam tip: identify \(a\), \(d\), and \(n\) before applying the AP sum formula.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Arithmetic Progressions (AP). Topic: Word problems based on APs.
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