WAEC 2022 Mathematics · Question 28
Solve - > 1
Options
- A.y < -10
- B.y < -2
- C.y < 2
- D.y < 10
Answer: B. y < -2
Explanation written with AI and checked against the answer key
Analyze the question: We need to find the values of y that satisfy the inequality (y+2)/4 − (y−1)/3 > 1.
Concept: To remove fractions, multiply both sides by the LCM of the denominators. Since the LCM is positive, the inequality sign stays the same. But if you multiply or divide by a negative number, the sign must flip.
Solution:
- The LCM of 4 and 3 is 12. Multiply every term by 12:
12(y+2)/4 − 12(y−1)/3 > 12(1)
- Simplify:
3(y+2) − 4(y−1) > 12
- Expand the brackets (be careful with the minus sign in front of the second bracket):
3y + 6 − 4y + 4 > 12
- Collect like terms:
−y + 10 > 12
- Subtract 10 from both sides:
−y > 2
- Divide by −1, which flips the sign:
y < −2
Check: Try y = −3 (which satisfies y < −2): (−3+2)/4 − (−3−1)/3 = −1/4 + 4/3 = (−3 + 16)/12 = 13/12, which is greater than 1. ✓
Try y = 0 (which does not satisfy it): 2/4 + 1/3 = 5/6, which is less than 1. ✓ (so it is correctly excluded)
Answer: y < −2, which is option B.
Tip: The most common mistakes here are forgetting to distribute the negative sign across (y−1) and forgetting to flip the inequality sign when dividing by a negative number. Always test a value from your answer to confirm.
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