A rectangular metal block measures 4.0 cm × 2.5 cm × 1.5 cm. If the mass of the block is 135 g, what is the density of the metal?
A$4.5 \ \text{g cm}^{-3}$
B$3.0 \ \text{g cm}^{-3}$
C$9.0 \ \text{g cm}^{-3}$CORRECT
D$6.0 \ \text{g cm}^{-3}$
GCEPhysicsMeasurement and Units2021
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Why the answer is C, and why the others tempt you.
Volume = 4.0 × 2.5 × 1.5 = 15.0 cm³. Density = mass ÷ volume = 135 ÷ 15.0 = 9.0 g cm⁻³. Common errors include computing volume incorrectly (e.g., summing dimensions) or dividing volume by mass instead.
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