Given,
Length of cylinder = 21 dm = 210 cm
Outer diameter = 10 cm
Outer radius = R = \(\frac{10}{2}\) = 5 cm
Inner diameter = 6 cm
Inner radius = r = \(\frac{6}{2}\) = 3 cm
∴ Area of base = π(R2 - r2) = π(25 - 9) = 16π cm2
Volume of cylinder = area of base x height = 16π x 210 = 16 x \(\frac{22}{7}\) x 210 = 10560 cm3