SOLUTION: cindy has 17 bills in her wallet. some are $10 bills and some are $20 bills. the total value of the bills are $230. how many $10 bills and how many $20 bills does she have?

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Question 1016199: cindy has 17 bills in her wallet. some are $10 bills and some are $20 bills. the total value of the bills are $230. how many $10 bills and how many $20 bills does she have?
Found 3 solutions by ikleyn, fractalier, Alan3354:
Answer by ikleyn(52776)   (Show Source): You can put this solution on YOUR website!
.
cindy has 17 bills in her wallet. some are $10 bills and some are $20 bills. the total value of the bills are $230.
how many $10 bills and how many $20 bills does she have?
--------------------------------------------------------------- 

Let x = # of $10 bills, and y = # of $20 bills.
Then you have the system of two equations in two unknowns

  x +   y =  17,   (1)
10x + 20y = 230.   (2)

Express x via y from equation (1): x = 17 - y, and substitute it into equation (2). You will get a single equation for y

10*(17-y) + 20y = 230.

Now simplify and solve:

170 - 10y + 20y = 230,

10y = 230 - 170 = 60.

y =  = 6.

Then x = 17 - y = 17 - 6 = 11.

Answer. 11 $10 bills and 6 $20 bills.


Answer by fractalier(6550)   (Show Source): You can put this solution on YOUR website!
Call the number of $10 and $20 bills, x and y. Then we have
x + y = 17 and the value equation is
10x + 20y = 230 Now multiply the top one by ten and subtract and get
-(10x + 10y = 170)
--------------------
10y = 60
y = 6 $20 bills
and then we must have
x = 11 $10 bills
Answer by Alan3354(69443)   (Show Source): You can put this solution on YOUR website!
cindy has 17 bills in her wallet. some are $10 bills and some are $20 bills. the total value of the bills are $230. how many $10 bills and how many $20 bills does she have?
-------------
t = # of 10's
w = # of 20's
--------
t + w = 17
10t + 20w = 230 --> t + 2w = 23
-----------
t + w = 17
t + 2w = 23
---------------- Subtract
-w = -6
--> 6 $20's
11 $10

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