Volume of the wood in the pen stand = Volume of cuboid – Total volume of three depressions.
Length of the cuboid (l) = 15 cm
Breadth of the cuboid (b) = 10 cm
Height of the cuboid (h) = 3.5 cm
Volume of the cuboid (V) = lbh = 15 × 10 × 3.5 = 525 cm3.
Radius of each depression (r) = 0.5 cm Height / depth (h) = 1.4 cm
Volume of each depressions V = \(\frac{1}{3
}\)πr2h
= \(\frac{1}{3
}\) × \(\frac{22}{7}\) × 0.5 × 0.5 × 1.4
= \(\frac{7.7}{3\times7}\) = \(\frac{1.1}{3}\) cm3
Total volume of the three depressions = 3 × \(\frac{1.1}{3}\) = 1.1 cm3
∴ Volume of the wood = 525 – 1.1 = 523.9 cm3