Question

A factory manufactures 120000 pencils daily. The pencils are cylindrical in shape each of length 25 cm and circumference of base as 1.5 cm. Determine the cost of colouring the curved surfaces of the pencils manufactured in one day at $Rs0.05perd{m}^2$.

Answer 1

Given, pencils are cylindrical in shape.
Length of one pencil= 25 cm.
And, circumference of base = 1.5 cm
(Circumference of circle=$2\pi r$)
$\Rightarrow r=\frac{1.5\times 7}{22\times 2}=0.2386cm$
Now, curved surface area of one pencil $=2\pi rh$
$=2\times \frac{22}{7}\times 0.2386\times 25$

$=\frac{262.46}{7}=37.49c{m}^2=\frac{37.49}{100}d{m}^2[\because 1cm=\frac{1}{10}dm]=0.375d{m}^2$
$\because$ Curved surface area of 120000 pencils $=0.375\times 120000=45000d{m}^2$
Now, cost of colouring $1d{m}^2$ curved surface of the pencils manufactured in one day $=Rs.0.05$
$\because$ Cost if colouring $45000d{m}^2$ $=45000\times 0.05=Rs.2250$