Question

the thickness of a hollow metallic cylinder is 2cm. It is 70cm long with outer radius of 14cm. Find the volume of the metal used in making the cylinder; assuming that it is open at both the ends. also find its weight if the metal weighs 8g per cm².

Answer 1

Thickness = 2cm
Length = height = 70cm
Outer radius (R) = 14 cm
Inner radius (r) = 14 - 2 cm
= 12cm
Volume = 2πrh + 2πRh + π (R^2 - r^2)
= 2x 22/7 x 12 x 70 + 2x22/7 x 14 x 70 + 22/7 (14^2 - 12^2)
= 5280 + 6160 + 22/7 [ ( 14+12)(14-12)]
= 11440 + 22/7 x 170
= 11440 + 534.285714
= 11974.2857 cm^3

Weight of metal in 1cm^3 = 8g
Weight of metal in 11974.2857 cm^3 = 11974.2857 x 8 = 95794.2856 g
If, it converts into kg then it would be = 95794.2856/1000
= 95.7942856 kg

Answer 2

This is a correct answer