# Determine the metal required to make a 21 m long pipe if its inner and outer diameter is 12 m and 10 m respectively ?

Determine the metal required to make a 21 m long pipe if its inner and outer diameter is 12 m and 10 m respectively ?

A. 725 m^{3}

B. 2534 m^{3}

C. 2843 m^{3}

D. 2647 m^{3}

**Answer : **A. 725 m^{3}

## Explanation:

### Find the volume with diameter = 12 m

Radius = Diameter ÷ 2

Radius = 12 ÷ 2 = 6 m

Volume = π * r^{2} * h

Volume = π * (6)^{2} * 21 **V _{1} = 2,375 m^{3}**

### Find the volume with diameter = 10 m

Radius = Diameter ÷ 2

Radius = 10 ÷ 2 = 5 m

Volume = π * r^{2} * h

Volume = π * (5)^{2} * 21 **V _{2} = 1650 m^{3}**

### Find the volume of the metal used:

Volume = V_{1} - V_{2}

= 2,375 - 1650

**Volume = 725 m ^{3}**