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
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)
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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