Word Problem

Question

Marry has 54 coins which are either 20 cent coins or 50 cent coins. If the total amount is $ 20.70, how many 20 cent coin does Marry have? 

Answer 1

x = 20 cent coins

y = 50 cent coins

 

x + y = 54

.20x + .50y = 20.70

 

Let's multiply the 2nd equation by 10 to clear decimals

x + y = 54

2x + 5y = 207

 

Multiply 1st equation by -2 and add equations to eliminate the x variable

 

-2x - 2y = -108

 2x + 5y = 207

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

        3y = 99

          y = 33

 

There are 33 of the 50 cent coins

There are 21 of the 20 cent coins

 

Check answer:

33(.5) + 21(.2) = 20.7

16.5 + 4.2 = 20.7

20.7 = 20.7

Answer is verified