WAEC Mathematics 2019 Objective — Question 5
Question 5 of 145 from the West African Examinations Council (WAEC) Mathematics 2019 Objective paper, with the correct answer and a full explanation.
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5. If 7 + y ≡ 4 (mod 8), find the least value of y, 10 ≤ y ≤ 30
- A. 11
- B. 13Correct
- C. 19
- D. 21
Explanation
7+y=4(mod 8) ⇒ y=−3(mod 8). Since negative values aren't allowed, add 8: y=5(mod 8), which doesn't fall in [10,30], so add 8 again: y=13, which falls within the range. Least value = 13.
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