Metal barrel

A barrel for transporting fuel has a height of 90 cm and a radius of the base of 30 cm. How many square meters of sheet metal are needed to make a barrel?

Correct answer:

S =  2.2619 m²

Step-by-step explanation:

$$\begin{gathered} h=90\text{cm}\to \text{m}=90:100\text{m}=0.9\text{m} \\ r=30\text{cm}\to \text{m}=30:100\text{m}=0.3\text{m} \\ {S}_1=\pi \cdot r^2=3.1416\cdot 0.3^2\doteq 0.2827{\text{m}}^2 \\ S=2\pi \cdot r\cdot h+2\cdot S_1=2\cdot 3.1416\cdot 0.3\cdot 0.9+2\cdot 0.2827=2.2619{\text{m}}^2 \end{gathered}$$

Try another example