Question

A closed cylindrical tank, made of thin iron-sheet, has diameter $8.4$ m and height $5.4$ m. How much metal sheet to the nearest $m^2$ is used in making this tank, if $\frac{1}{15}$ of the sheet actually used was wasted in making the tank ?

• A. $272m^2$
• B. $270m^2$
• C. $235m^2$
• D. $240m^2$

Answer 1

The correct option is B $270m^2$

Given diameter $=8.4$ m
We know, diameter $=2\times$ radius
$\therefore$ radius $=4.2$ m
Also given, height $=5.4$ m
$\therefore$ total surface area of cylinder $=2\pi r(r+h)c{m}^2$
$=2\left(3.14\right)\left(4.2\right)(4.2+5.4)=253.44$
$\frac{1}{15}$ of the sheet is used was wasted to making the tank $=\frac{1}{15}\times 253.44=16.896$
$\therefore$ total metal sheet used in making tank $=253.44+16.896=270.336m^2$ $=270m^2$