Question

A man purchased 47 stamps of 20 p and 25 p for ₹10. Find the number of each type of stamps.

Answer 1

Let the number of stamps of 20 p and 25 p be x and y respectively.
As per the question
$$\begin{gathered} x+y=47.....\left(i\right) \\ 0.20x+0.25y=10 \\ 4x+5y=200.....\left(ii\right) \end{gathered}$$
From (i), we get
$y=47-x$
Now, substituting $y=47-x$ in (ii), we have
$$\begin{gathered} 4x+5\left(47-x\right)=200 \\ \Rightarrow 4x-5x+235=200 \\ \Rightarrow x=235-200=35 \end{gathered}$$
Putting x = 35 in (i), we get
$$\begin{gathered} 35+y=47 \\ \Rightarrow y=47-35=12 \end{gathered}$$
Hence, the number of 20 p stamps and 25 p stamps are 35 and 12 respectively.