(b) 192
Explanation:
The length, breadth & height of a rectangular hole are 40 m, 12 m & 16 m respectively volume = (40 × 12 × 16) m3.
And the length, breadth & thickness of a rectangular wooden plank are 5 m, 4 m & 2 respectively.
∴ Its volume = (5 × 4 × 2) m3
∴ No. of planks =\frac{40 × 12 × 16}{5 × 4 × 2}= 12 × 16 = 192