WAEC 2011 Mathematics · Question 43
Simplify 1
Options
- A.3
- B.2
- C.-4
- D.-5
Answer: C. -4
Explanation written with AI and checked against the answer key
Analyze the question: We need to simplify 1¾ − (2⅓ + 4). Work out the bracket first, then subtract.
Concept: Follow BODMAS (brackets first). Convert mixed numbers to improper fractions, or work with whole numbers and fractions separately, using a common denominator.
Solution:
Step 1: Bracket 2⅓ + 4 = 6⅓
Step 2: Subtract 1¾ − 6⅓
Convert to improper fractions with denominator 12:
- 1¾ = 7/4 = 21/12
- 6⅓ = 19/3 = 76/12
21/12 − 76/12 = −55/12
Step 3: Convert back to a mixed number 55 ÷ 12 = 4 remainder 7, so −55/12 = −4 7/12
Answer: −4 7/12, which is option C.
Tip: When you subtract a bigger number from a smaller one, the answer is negative. Here 6⅓ is clearly bigger than 1¾, so you should expect a negative result. That lets you eliminate options A and B straight away. Always do the bracket first, and check your sign before choosing an option.
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