Question

Question 4
The barrel of a fountain pen, cylindrical in shape, is 7 cm long and 5 mm in diameter. A full barrel of ink in the pen is used up on writing 3300 words on an average. How many words can be written in a bottle of ink containing one fifth of a litre?

Answer 1

Given length of the barrel of a fountain pen = 7 cm
And diameter
$=5mm=\frac{5}{10}cm(10mm=1cm)=\frac{1}{2}cm$

Volume of the barrel $=\pi r^{2}h$
[Since, its shape is cylindrical]
$=\frac{22}{7}\times (0.25{)}^2\times 7(radius=.025cm)=22\times 0.0625=1.375c{m}^3$

Also given volume of ink in the bottle = $\frac{1}{5}$ of litre $=\frac{1}{5}\times 1000c{m}^3=200c{m}^3$ (1 litre= 1000$c{m}^3$)

Now $1.375c{m}^3$ ink is used for writing number of words = 3300

$\therefore 1c{m}^3$ ink is used for writing number of words
$=\frac{3300}{1.375}$

$\therefore 200c{m}^3$ ink is used for writing number of words
$=\frac{3300}{1.375}\times 200=480000$