Question

how much iron is needed to make a rod of length 10 cm and diameter 1.4 CM​

Answer 1

Given :

• Length of rod = 10 cm
• Diameter of rod = 1.4 cm

To find :

• Iron needed to make the rod of length 10 cm and diameter 1.4 cm

Concept :

Firstly, calculate the radius of the rod. By using the formula to calculate radius when diameter is given. Then substitute the values in the formula of volume of cylinder to calculate the amount of iron needed to make the rod.

➳ Formula to calculate radius, when diameter is given :-

• Radius = Diameter ÷ 2

➳ Formula to calculate volume of cylinder, when radius and height of cylinder is given :-

• Volume of cylinder = πr²h

where,

• Take π = 22/7
• r = radius
• h = height

Solution :

Using formula,

★ Radius = Diameter ÷ 2

Substituting the given values,

→ Radius = 1.4 ÷ 2

→ Radius = 0.7

Radius of the cylinder = 0.7 cm

Using formula,

★ Volume of cylinder = πr²h

Substituting the given values,

→ Volume = 22/7 × (0.7)² × 10

→ Volume = 22/7 × 7/10 × 7/10 × 10

→ Volume = 22 × 7/10

→ Volume = 154/10

→ Volume = 15.4

Volume of the cylinder = 15.4 cm³

Therefore,

• 15.4 cm³ of iron is needed to make a rod of length 10 cm and diameter 1.4 cm.