an all day parking meter takes only dimes and quarters. if it contains 100 coins with a total value of $14.50, how many of each type of coin are in the meter?

Question

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Answer 1

Two equations with 2 unknowns

 

d= number of dimes

q= number of quarters

 

d+q=100   so q=100-d

10d +25q = 1450

 

substitute 100-d for q

 

10d + 25(100-d) = 1450

10d + 2500 - 25d = 1450  (oops, going to be negative, but not a problem)

-15d = -1050

d=70

q=30

 

An easier way is to assume all 100 are dimes, but that only totals $10.00.  Each "upgrade" of a dime to a quarter adds 15 cents, so to add the extra $4.50, you'd need to "upgrade" 30 dimes to quarters.  same answer, but that's not the way your teacher wanted you to do it.