A line graph of cost vs. number of pens shows: $1$ pen costs $\rupee\,5$, $2$ pens cost $\rupee\,10$, $3$…
A line graph of cost vs. number of pens shows: $1$ pen costs $\rupee\,5$, $2$ pens cost $\rupee\,10$, $3$ pens cost $\rupee\,15$. The cost of $7$ pens is:
$\rupee\,30$
$\rupee\,32$
$\rupee\,35$
$\rupee\,40$
Solution
Cost is directly proportional, $\rupee\,5$ per pen. $7 \times 5 = 35$.