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Dennis mowed his next door neighbor's lawn for a handful of dimes and nickels, 80 coins in all.
Upon completing the job he counted out the coins and it came to to $6.60.
how many of each coin did he earn?
Let n = no. of nickels; let d = no. of dimes
The no. of coins equation:
n + d = 80
n = (80-d), use this for substitution in the value equation
The total value equation
.05n + .10d = 6.60
Replace n with (80-d)
.05(80-d) + .10d = 6.60
4 - .05d + .10d = 6.60
-.05d + .10d = 6.60 - 4
.05d = 2.60
d = 2.6/.05
d = 52 dimes
80 - 52 = 28 nickels
See if that come out right
.05(28) + .10(52) =
1.40 + 5.20 = 6.60 confirms our solution of 28 nickels and 52 dimes