Question

An iron pipe $20cm$ long has exterior diameter equal to $25cm$. If the thickness of the pipe is $1cm$, find the whole surface area of the pipe.

• A. $3167c{m}^2$
• B. $3160c{m}^2$
• C. $3068c{m}^2$
• D. $3268c{m}^2$

Answer 1

The correct option is A $3167c{m}^2$

TSA of pipe $=$ $2\pi h(R+r)+2\pi (R^2-r^2)$

$=$ $2\times \frac{22}{7}\times 20(12.5+11.5)+2\times \frac{22}{7}({\left(12.5\right)}^2-{\left(11.5\right)}^2)$

$=$ $\frac{44\times 480}{7}+\frac{44\times 24}{7}$

$=$ $\frac{21120}{7}+\frac{1056}{7}=\frac{22176}{7}$

$=$ $3167$ ${cm}^2$