MathematicsProgressionsWAEC
The sum of the first n terms of the arithmetic progression 3, 5, 7, ... is 120. Find n.
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Answer: B. 10
Sₙ = n/2 × (6 + 2(n − 1)) = n(n + 2) = 120, so n = 10.
An AdmitMe practice question, written for the WAEC syllabus. Not an official past question.