The sum of the first (12) terms of an arithmetic progression is (516) and the (12)th term is (75). What is the first term?
Answer and explanation
Correct answer: (11)
Using (S_n=\frac{n}{2}(a+l)), (516=6(a+75)), so (a=11). Exam tip: when the last term is given, use the (a+l) form.
Frequently asked questions
What is the correct answer to this question?
(11)
Why is this the correct answer?
Using (S_n=\frac{n}{2}(a+l)), (516=6(a+75)), so (a=11). Exam tip: when the last term is given, use the (a+l) form.
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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