Answer :

**Concept Used:** Volume of the wood = Volume of a pencil – volume graphite

Volume of Cylinder = πr^{2}h

Where r = radius of the cylinder and h = height of the cylinder

**Given:** Diameter of pencil = 7 mm

Diameter of graphite = 1 mm

Length of the pencil = 14 cm

**Assumption:** Let r_{1} be the radius of pencil, r_{2} be the radius of graphite and h be the height of pencil.

**Explanation: **

Radius

Radius (pencil), r_{1} mm = 0.35 cm

Radius (graphite), r_{2} mm = 0.05 cm

Height (Pencil), h = 14 cm

Volume of wood in pencil = π (r_{1}^{2} – r_{2}^{2}) h

= 22/7 [(0.35)^{2} – (0.05)^{2} × 14]

= 22/7 (0.1225 – 0.0025) × 14

= 44 × 0.12

= 5.28 cm^{3}

Volume of graphite = πr_{2}^{2}h

= 22/7 × (0.05)^{2} × 14

= 44 × 0.0025

= 0.11 cm^{3}

**Hence, The volume of wood in pencil is 5.28 cm ^{3} and volume of graphite in pencil is 0.11 cm^{3}.**

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