Dollar Bills and system of two linear equations
by Kendall Whiteside
(Happy Valley, Oregon)
“A student has some $1 bills and $5 bills in his wallet. He has a total of 15 bills that are worth $47. How many of each type of bill does he have? ”
Let x be the number of $1 bills and y be the number of $5 bills.
The number of $1 bills plus the number of $5 bills equal 15 or x + y = 15
Worth of $1 bills plus worth of $5 bills = $47 or 1x + 5y = 47
Therefore, just solve the system of equations below.
x + y = 15 (1)
x + 5y = 47 (2)
(2) minus (1) will give 4y = 32
y = 8 since 4 × 8 = 32
x + 8 = 15
x = 7
The student has seven $1 bills and eight $5 bills.
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Sep 17, 20 03:57 PM
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