SOLUTION: An office has some 20 cent stamps and some 28 cent stamps. All together the office has 140 stamps for a total value of $31.20. How many of each stamp does the office have?
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Question 192256This question is from textbook Intermediate Algebra
: An office has some 20 cent stamps and some 28 cent stamps. All together the office has 140 stamps for a total value of $31.20. How many of each stamp does the office have?
my try:
Stamps Number Value Total Value
20 cent x .20 .20x
28 cent 140 -x .28 .28(140-x)
.20x + .28(140-x) = 31.20
.20x + 39.20 - .28x = 31.20
.08x + 39.20 = 31.20
-.08x = -8.00
x = 1
WRONG? What am I doing wrong?? Help!
This question is from textbook Intermediate Algebra
Found 2 solutions by Mathtut, radikrr:
Answer by Mathtut(3670) (Show Source): You can put this solution on YOUR website!
let the number of 20 cent and 28 cent stamps by x and y respectively
:
x+y=140........eq 1
.2x+.28y=31.2..eq 2
:
rewrite eq 1 to x=140-y and plug it into eq 2
:
.2(140-y)+.28y=31.2
:
28-.2y+.28y=31.2
:
.08y=3.2
:
y=40 (28 cent stamps)
:
x=140-y=140-40=100 (20 cent stamps)
Answer by radikrr(7) (Show Source): You can put this solution on YOUR website!
An office has some 20 cent stamps and some 28 cent stamps. All together the office has 140 stamps for a total value of $31.20. How many of each stamp does the office have?
my try:
Stamps Number Value Total Value
20 cent x .20 .20x
28 cent 140 -x .28 .28(140-x)
.20x + .28(140-x) = 31.20
.20x + 39.20 - .28x = 31.20
.08x + 39.20 = 31.20
-.08x = -8.00
x = 800/8 =100
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