SOLUTION: Bob has 20 coins totaling $1.20. If he has only dimes and nickels, how many of each coin does he have?

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Question 1157299: Bob has 20 coins totaling $1.20. If he has only dimes and nickels, how many of each coin does he have?
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

let the number of dimes be d and nickels n
if Bob has 20+coins, then
d%2Bn=20 .....solve for d
d=20-n.....eq.1
if he has total $1.20, then
0.10d%2B0.05n=1.20......substitute d from eq.1
0.10%2820-n%29%2B0.05n=1.20.....solve for n
0.10%2820-n%29%2B0.05n=1.20....both sides multiply by 100 to get rid of decimals
10%2820-n%29%2B5n=120
200-10n%2B5n=120
200-5n=120
200-120=5n
80=5n
n=80%2F5
n=16
go to eq.1
d=20-n.....eq.1, ...substitute n
d=20-16
d=4
answer: Bob have 4 dimes and 16 nickels