A man buys postage stamps of denominations $3$ paise and $5$ paise, for Rs $1$. He buys $22$ stamps in all. Find the number of $3$ paise stamps bought by him. (100p= 1 Rs)
I tried, Let the number of 3 p coins be $x$
Let the number of 5 p coins be $y$
Total cost $=$ Rs $1.00 = 100$ paise
$$3x + 5 y = 100 \tag{1}$$
What should be the second equation?
HINT:
$p+q=22$
and
$3p+5q=100$ (yes, because 1 Rs. = 100 paise! and not other way round)
where, $p$ is the number of 3 paise stamps and $q$ is the number of 5 paise stamps.
Thats, 2 equation and 2 unknown, how hard is that?