Set up and solve algebraically!
Using 32-cent, 20-cent and 7-cent stamps, Rob put $10.08 of postage on a large package. He used twice as many 32-cent stamps as 20-cent stamps and three times as many 7-cent stamps as 32-cent stamps. How many of each type of stamp did he use?
Let x = # of 20-cent stamps
Let y = # of 32-cent stamps
Let z = # of 7-cent stamps
So, we have the equation:
.20x + .32y + .07z = 10.08
Upon further review, we can say that:
the # of 32-cent stamps, y = 2x
.20x + .32(2x) + .07(6x) = 10.08 <<mult by 100>>
20x + 32(2x) + 7(6x) = 1008 <<simplify each term>>
20x + 64x + 42x = 1008 <<combine like terms>>
126x = 1008
x = 1008/126
x = 8
therefore, Rob used:
Check your answer in the original problem:
.20(8) + .32(16) + .07(48) = 10.08
1.60 + 5.12 + 3.36 = 10.08 TRUE!