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 2 cm, 90 cm and 30 cm respevtively.How many balls were melted to make the tube??!

Answer 1

Outer radius of the drum =30=R
Thickness of the drum=2cm
Inner radius of the drum=30-2=28
Height of the drum=90cm=h
Volume of the plastic required to make a drum
=πR²h-πR²h+πR²×2
=π (R²h-R²h+2r²)
=π (30²×90-28²×90+2×28²)
=π (81000-70560+1568)
=π×12008
Volume of a spherical plastic ball
4/3×π×1³
4π/3
Numbers of ball required to make the drum
π×12008/4π/3
12008×3/4
9006

Answer 2

outer radius of the drum = 30 =R
thickness of the drum = 2cm
inner radius of the drum = 30 - 2 = 28
height of the drum = 90 cm
volume of the plastic to required a drum
=πR^2h-πR^2 h+πR^2×2
=π[R^2h-R^2h+2R^2]
=π(30^2×90-28^2×90+2×28^2
=π(81000-70560+1568)
=π×12008
volume of a spherical plastic ball
4/3×π×1^3
4π/3
number of balls required to make the drum
=π×12008/4π/3
=12008×4/3
=9006
hope it helps!