WAEC Mathematics 2025 Theory — Question 15
Question 15 of 19 from the West African Examinations Council (WAEC) Mathematics 2025 Theory paper, with the correct answer and a full explanation.
Advertisement
12(a). The eighth term of an Arithmetic Progression (A.P.) is 46 and the sum of the first eight terms is 200. Find the: (i) first term; (ii) sum of the first 12 terms.
Model answer
(i) T₈ = a + 7d = 46 ...(1) S₈ = (8/2)(2a + 7d) = 200 2a + 7d = 50 ...(2) (1)−(2): a − 7d + 7d − 2a = 46 − 50 ... subtract Solving: a = 4, d = 6 (ii) S₁₂ = (12/2)[2(4)+(12−1)×6] = 6[8 + 66] = 6×74 = 444
Advertisement
Sign up free to unlock
- Score tracking
- Practice history
- Saved questions
- Progress dashboard
- Personalized sessions
- Weak-topic breakdown
…and/or go further with premium services and No Ads.