Question 1137180: Manny is always looking for coins lost on the playground. He has a collection of 72 coins, all nickels and dimes, that totals $6.20. What is the total amount of money he has found in dimes?
Answer by greenestamps(13203)   (Show Source):
You can put this solution on YOUR website!
(1) Algebraically....
d+n = 72 [the total number of dimes and nickels is 72]
10d+5n = 620 [the total value of the coins (in cents) is 620]
Solve by any method you want (I think elimination is by far the easiest....)
(2) Using logical reasoning....
If all 72 coins were dimes, the total value would be 720 cents; that's 100 cents more than the actual total.
Each nickel is worth 5 cents less than each dime. For the total value of the coins to be 100 cents less than 720, the number of nickels has to be 100/5 = 20.
ANSWER: 20 nickels and the rest (52) dimes.
Assuming this problem comes from a beginning algebra course, you of course should understand how to solve the problem using formal algebra.
But solving problems like this through logical reasoning can be very good brain exercise....
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