Question

A metal pipe has a bore (inner diameter) of 5 cm. The pipe is 5 mm thick all round. Find the weight, in the kilogram, of 2 meters of the pipe if 1 $c{m}^3$ of the metal weighs 7.7 g.

• A. 12.31 kg
• B. 13.31 kg
• C. 19.31 kg
• D. 14.31 kg

Answer 1

Answer: (B)

Inner diameter=5 cm. radius=2.5cm
thickness =5mm=0.5cm
outer radius=2.5+0.5=3cm
length=2m=200cm
volume of pipe=
$V=\Pi {(R}^2-r^2)h$
$V=3.14{(3}^2-{2.5}^2)\ast 200$
$V=22/7\ast (9-6.25)\ast 200$
$V=12100/7{cm}^3$
1 $c{m}^3$ of the metal weighs 7.7 $g$.
$So,\frac{12100}{7}c{m}^{3}weighs=7.7\ast \frac{12100}{7}gm=13310gm=13.31kg$