Question

The barrel of a fountain pen, cylindrical in shape, is $7cm$ long and $5mm$ in diameter. A full barrel of ink in the pen is used up on writing $3300$ words on an average. If $k$ words can be written in a bottle of ink containing one fifth of a litre, find $\frac{k}{1000}$.

Answer 1

Volume of ink in pen $=\pi r^{2}h=\pi \left(0.5{)}^2\right(7)=5.5c{m}^3.$
$\frac{1}{5}$ of $1$ litre $=\frac{1}{5}\times 1000c{m}^3=200c{m}^3$
$200c{m}^3$ of ink $=\frac{\left(200\right)\left(3300\right)}{5.5}=120,000$ words

$\therefore k=\mathrm{120,000}$

$\Rightarrow \frac{k}{1000}=120$