Question

You have a total of 21 coins, all nickels and dimes. The total value is $1.70. Write and solve a system of equations to find the number of dimes d and the number of nickels n that you have.

Answer 1

To solve this problem you must apply the following proccedure:

 1. You have a total of 21 coins, all nickels and dimes. Then:

 x:nickels=5 cents
 y: dimes=10 cents

 x+y=21

 2. You have that the total value is $1.70. Then:

 5x+10y=170

 3. The system of equation is:

 x+y=21    (i)
 5x+10y=170    (ii)

 4. You have:

 x+y=21
 x=21-y

 5(21-y)+10y=170
 105-5y+10y=170
 y=13 dimes

 x+13=21
 x=8 nickels