Tim bought some 25¢ and some 29¢ stamps. He paid $7.60 for 28 stamps. How many of each type of stamp did he buy?

Question

I don't know how to format this into an equation. 

Answer 1

Hello Tabitha, 

 

Let x be the stamps that cost 25 ¢ and y that cost 29¢

 

x + y = 28

 

25x + 29y = 760   because  $1 = 100 ¢

 

 

Plug  x = 28 - y into the second equation

 

25(28 - y) + 29y = 760

700 -25y +29y =760

                 4y = 760-700

                   y = 60/4

y = 15 and x = 28-15 = 13

 

You have 13 stamps that cost 25¢ each and 15 stamps each cost 29¢

 

 

Answer 2

Let n be the number of 25 cent stamps.

Then, 28 - n must be the number of 29 cent stamps.

Tim paid $7.60 the stamps.

 

0.25n + 0.29(28 - n) = 7.60

 

This means that n stamps at 25 cents a piece plus (28 - n) stamps at 29 cents a piece sum to $7.60.

 

Solve for m.

 

0.25n + 8.12 - 0.29n = 7.60

 

-0.04n = -0.52

 

n = 13

 

So, Tim bought 13 25-cent stamps and 28 - 13 = 15 29-cent stamps