2015 · Q83
A rectangular block of wood having dimensions 3m x 2m x 175m has to be painted on all its faces. The layer of paint must be 0.1 mm thick. Paint comes in cubical boxes having their edges equal to 10 cm. The minimum number of boxes of paint to be purchased is
Elementary MathematicsMensuration
- A5
- B4
- C3
- D2
Explanation
Surface = 2(3·2 + 2×1.75 + 3×1.75) = 29.5 m²; paint volume = 29.5 × 10⁻⁴ m³ = 2950 cm³; each 1000 cm³ box covers 1000 cm³, so ⌈2.95⌉ = 3 boxes (option C).