Question

some plastic balls of radius 1 cm were melted and cast into a tube. The thickness, length and outer radius of the tube were 2cm, 90cm, and 30 cm respectively. how many balls were melted to make the tube?

Answer 1

the numbers of balls required will be 7830

Answer 2

Given :

• Radius of plastic balls = 1m

• The thickness, length and outer radius of the tube were 2cm, 90cm, and 30 cm respectively.

• Inner radius = 30 - 2 = 28 m

To find :

- Number of balls were melted to make the tube

Solution :

• Let number of balls melted be n

We know that,

n×volume of balls = volume of tube

n×(4/3)×pi×r^3 = pi×[ R'^2 - R^2 ]×h

n×(4/3)×1 = ( 30^2 - 28^2 )×90

4n/3 = 58×2×90

n = 58×2×90×3 / 4

n = 87×90

n = 7830