NCERT Exemplar Solutions
Class 10 - Mathematics - CHAPTER 12: Surface Areas & Volumes - Exercise 12.3
Question 12

Question. 12

How many spherical lead shots of diameter 4 cm can be made out of a solid cube of lead whose edge measures 44 cm?

Answer:

2541 shots

Detailed Answer with Explanation:

Step 1: Find the volume of the cube.

The formula for the volume of a cube is:

\( V = a^3 \), where \(a\) is the length of the edge.

Here, \( a = 44\,\text{cm} \).

So, volume of cube = \( 44^3 = 85184\,\text{cm}^3 \).


Step 2: Find the volume of one spherical lead shot.

We are told the diameter of each spherical shot = 4 cm.

So, radius \( r = \dfrac{4}{2} = 2\,\text{cm} \).

Formula for volume of a sphere is:

\( V = \dfrac{4}{3} \pi r^3 \).

Substitute \( r = 2 \):

\( V = \dfrac{4}{3} \pi (2)^3 = \dfrac{4}{3} \pi \times 8 = \dfrac{32}{3} \pi \).

So, the volume of one spherical shot = \( \dfrac{32}{3}\pi\,\text{cm}^3 \).


Step 3: Find the number of shots.

Total number of shots = (Volume of cube) ÷ (Volume of one sphere)

= \( \dfrac{85184}{(32/3)\pi} \).

= \( \dfrac{85184 \times 3}{32 \pi} \).

= \( \dfrac{255552}{32 \pi} \).

= \( \dfrac{7986}{\pi} \).

Now, using \( \pi \approx 3.1416 \):

\( \dfrac{7986}{3.1416} \approx 2541 \).


Final Answer:

The cube of lead can be melted to make 2541 spherical shots.

NCERT Exemplar Solutions Class 10 – Mathematics – CHAPTER 12: Surface Areas & Volumes – Exercise 12.3 | Detailed Answers