How would you solve the following using a table? Andrew cashes a $180 check and wants the money in $10 and $20 bills. The bank teller gives him 12 bills. How many of each kind of bill does he receive?

1 Answer
Nov 26, 2014

We can solve this problem using a table and a pair of linear equations.

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(The dollar sign has been disregarded.)

Now, we know that he has received a total amount of $180. Thus, our first equation is:

#10x+20y=180# --------(1)

Now, we need another equation. We know that he has received 12 bills in total. Therefore, our second equation is:

#x+y=12#

To make at least one variable term exactly like in the first equation, I will multiply this equation by 10, getting:

#10x+10y=120# --------(2)

Subtracting equation (2) from (1),

#(+)10x+20y=180#
#(-) 10x+10y=120#
#---------#
#(=) 0 +10y=60#

Therefore, #y=60/10#

#y=6#

Substituting #y=6# in (2),

#10x+10(6)=120#
#10x+60=120#
#10x=120-60#
#10x=60#

#x=60/10#

#x=6#

Thus, we can conclude that he receives 6 bills each of $10 and $20.