Question 140417: A cahshier had to give sarah $3.45 in change but he had only quarters and dimes in the register. If he gave her 15 coins, how many dimes did she recieve?
Answer by jojo14344(1513)   (Show Source):
You can put this solution on YOUR website! First, let us assign "x"= # of quarters and "y"= # of dimes.
As per given, total # of quarters and dimes given equals 15. To show,
x+y=15, right? Remember this as equation 1.
Now,when we multiply quarter(0.25) by the # of coins "x" plus dimes(0.10) multiplied by # of coins "y" we get $3.45 as the total change right? To show,
0.25x+0.10y=$3.45, remember this as equation 2 now.
Go back to equation 1, we get y=15-x. Then substitue this value of y to equation 2. To show,
0.25x+0.10(15-x)=$3.45
0.25x+1.5-0.10x=$3.45
0.15x=3.45-1.5
x=13, this will the # of quarters
For the # of dimes,
y=15-x=15-13
y=2 (# of dimes)
Simply to check refer to equation 2,
0.25(13)+0.10(2)=$3.45
$3.25+$0.20=$3.45
$3.45=$3.45
Cool!
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