# Thread: stamps problem

1. ## stamps problem

hello

we bought 100 stamps with total cost of 100 dollars
the stamps are priced at 5, 3, and 0.5 dollars

how many stamps of each price do we bought?

can you solve it with equations and with logical/practical calculations?

thanks

2. Originally Posted by mathos
hello

we bought 100 stamps with total cost of 100 dollars
the stamps are priced at 5, 3, and 0.5 dollars

how many stamps of each price do we bought?

can you solve it with equations and with logical/practical calculations?

thanks
$5 stamps = a$3 stamps = b
$0.50 stamps = c$\displaystyle 5a+3b+0.5c = 100\displaystyle a+b+c = 100$Not sure where to go from there 3.$5 stamps = a
$3 stamps = b$0.50 stamps = c

(1)
(2)
(2) divided by 2:
(3) $\displaystyle \frac {a}{2} + \frac {b}{2}+0.5c=50$
Hence,
$\displaystyle 0.5c= 50-\frac {a}{2}-\frac {b}{2}$
Substituting this into equation (1) will give:
$\displaystyle 5a + 3b + 50-\frac {a}{2}-\frac {b}{2}=100$
Which will eliminate c from one equation...I don't think that it can be done for another, which would then have allowed you to solve simultaneously because you only have 2 equations but 3 unknowns.