Question

A man buys postage stamps of denominations 25 paisa and 50 paisa for Rs.10. he buys 28 stamps in all. Find the number of 25 paisa stamps bought .​

Answer 1

Let the man buys x 25 paisa stamps and y 50 paisa stamps. Then

x+y=28 .........(1)

and 0.25x+0.5y=10

or

4

1

x+

2

1

y=10

or

4

x+2y

=10

x+y=40 .........(2)

Subtract equation (1) from equation (2)

x+2y=40

+x+y=28

(−)(−)(−)

y=12

∴x=28−12=16