WAEC 2023 Mathematics · Question 25
m:n = and n : q = , find q : m.
Options
- A.35 : 18
- B.16 : 35
- C.18 : 35
- D.35 : 16
Answer: B. 16 : 35
Explanation written with AI and checked against the answer key
Step 1: Convert to improper fractions
- m : n = 7/3 : 6/5
- n : q = 3/2 : 4/3
Step 2: Simplify each ratio to whole numbers
- m : n = 7/3 : 6/5. Multiply both sides by 15: 35 : 18.
- n : q = 3/2 : 4/3. Multiply both sides by 6: 9 : 8.
Step 3: Make n the same in both ratios
n is 18 in the first ratio and 9 in the second. Multiply the second ratio by 2: n : q = 18 : 16.
So m : n : q = 35 : 18 : 16.
Step 4: Find q : m
q : m = 16 : 35
Check: m/n = 35/18 and n/q = 9/8. Then m/q = (35/18)(9/8) = 315/144 = 35/16, so q/m = 16/35. ✓
Answer: B (16 : 35)
Tip: When chaining ratios, clear the fractions first. Then scale the shared term (here n) so it matches in both ratios, and join them into one ratio such as m : n : q. Read off the pair you need, and watch the order, since the question asks for q : m, not m : q.
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