Question

A printer can print 68 lines per minute. How many lines can it print in an hour?

Answer 1

$\large\underline{\sf{Solution-}}$

Given that,

A printer can print 68 lines per minute.

Now, we have to find ow many lines can it print in an hour. i.e how many lines can it print in 60 minutes.

So, more time, more lines can be printed.

It means, number of lines printed is in direct variation with time taken.

So, Let assume that number of lines printed in 60 minutes be x.

$\begin{array}{|c|c|c|c} \hline \rm Number \: of \: lines&\rm 68&\rm x \\ \hline\rm Time \: taken \: (in \: minutes)&\rm 1&\rm 60 \\ \hline \end{array}$

So, using Law of direct variation, we have

$\rm \: \dfrac{68}{1} = \dfrac{x}{60}$

$\rm \: x = 68 \times 60$

$\rm\implies \:\boxed{ \rm{ \:x = 4080 \: }}$

$\rule{190pt}{2pt}$

Alternative Method :-

$\rm \: In \: 1 \: minute, \: number \: of \: lines \: printed = 68$

So,

$\rm \: In \:60\: minute, \: number \: of \: lines \: printed = 68 \times 60 = 4080$