WAEC 2024 Mathematics · Question 5
The length and breadth of a cuboid are 15 cm and 8 cm respectively. If the volume of the cuboid is 1560 cm, calculate the total surface area.
Options
- A.976cm
- B.838cm
- C.792cm
- D.746cm
Answer: B. 838cm
Explanation written with AI and checked against the answer key
Step 1: Analyze the question We have a cuboid with length l = 15 cm, breadth b = 8 cm and volume V = 1560 cm³. We must find the height first, then the total surface area.
Step 2: Concept
- Volume = l × b × h
- Total surface area = 2(lb + lh + bh)
Step 3: Solution
Find the height: 15 × 8 × h = 1560 120h = 1560 h = 13 cm
Now the surface area:
- lb = 15 × 8 = 120
- lh = 15 × 13 = 195
- bh = 8 × 13 = 104
Sum = 120 + 195 + 104 = 419
Total surface area = 2 × 419 = 838 cm²
Step 4: Answer
Tip: In cuboid problems, always find the missing dimension from the volume first. Then use 2(lb + lh + bh) and add the three pair-areas before doubling, which helps avoid arithmetic slips. Also, 120 × 13 = 1560 is a quick check on h.
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