2 cubes each of volume 64 cm³ are joined end to end. The surface area of the…
2022
2 cubes each of volume 64 cm³ are joined end to end. The surface area of the resulting cuboid is –
- A.
128 cm²
- B.
140 cm²
- C.
150 cm²
- D.
160 cm²
Attempted by 3 students.
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Correct answer: D
Key idea: find the cube side, form the cuboid dimensions, then use the surface area formula.
Step 1: Determine the side of each cube: cube root of 64 is 4, so side = 4 cm.
Step 2: When joined end to end, dimensions of the resulting cuboid are 8 cm × 4 cm × 4 cm.
Step 3: Use the surface area formula for a cuboid: SA = 2×(length×width + length×height + width×height).
Step 4: Substitute the numbers: SA = 2×(8×4 + 8×4 + 4×4) = 2×(32 + 32 + 16) = 2×80 = 160 cm².
Answer: 160 cm²