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 cm3^3, calculate the total surface area.

Options

  1. A.976cm2^2
  2. B.838cm2^2
  3. C.792cm2^2
  4. D.746cm2^2

Answer: B. 838cm2^2

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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