Question 70

The volume of a metallic cylindrical pipe is 7480 cm$$^3$$ . If its length is 1.4 m and its external radius is 9 cm, then its thickness (given $$\pi = \frac{22}{7}$$) is:

Solution

As per the question,

The volume of the cylindrical pipe $$=\pi (R^2-r^2)h$$

R is the external radius of the pipe and r is the internal radius of the pipe.

So, $$7480=\pi (9^2-r^2)\times 140$$

$$\Rightarrow \dfrac{7480}{140\times pi}=9^2-r^2$$

$$\Rightarrow r^2=9^2-17=64$$cm

$$\Rightarrow r=8cm$$

Hence the thickness of the pipe=9-8=1cm

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