Hi, 

I need to write 2 equations and solve by addition method

in that case, let x = number of dimes and y = number of quarters

x   +   y = 32

10x + 25y = 650 cents

Multiplying both sides of the first equation by -25 to eliminate y

-25x -25y = 32*(-25)

10x + 25y = 650 cents

-15x = -150

x = 10, the enumber of dimes

the quarters would be 22 (32-10)



checking our answer

10*10 + 22*25 = 100 + 550 = 650cents Or $6.50 

Answer by nerdybill(7384)   (Show Source): You can put this solution on YOUR website!
 Audrey has 32 dimes and quarters in her piggy bank with a total value of 6.50. How many of the coins are dimes and how many are quarters? 

I need to write 2 equations and solve by addition method

.

Let x = number of dimes

and y = number of quarters

.

From: "Audrey has 32 dimes and quarters in her piggy bank"

x + y = 32 (equation 1)

.

From: "total value of 6.50"

.10x + .25y = 6.50 (equation 2)

.

Using the "addition method", to eliminate x, we multiply both sides of equation 1 by -.10 and "add" the two equations together:

-.10x - .10y = -3.2

.10x + .25y = 6.50

----------------------

      .15y = 3.3

y = 22 (number of quarters)

.

Substitute the above value of y back into equation 1 to find x:

x + y = 32

x + 22 = 32

x = 32-22

x = 10 (number of dimes)

 

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