SOLUTION: The freshman class treasury has 30 ten- and twenty-dollar bills that have a total value of $430. How many of each bill do they have?

Question 1181289: The freshman class treasury has 30 ten- and twenty-dollar bills that have a total value of $430. How many of each bill do they have?
Found 2 solutions by josgarithmetic, greenestamps:
Answer by josgarithmetic(39627) (Show Source): You can put this solution on YOUR website!
Thirty bills, t the number of twenty-dollar bills
, to account for the money value of the combined bills

.
.
Answer by greenestamps(13206) (Show Source): You can put this solution on YOUR website!

A quick and easy mental solution, if formal algebra is not required....

(1) Imagine having 30 bills that were all $10 bills. The total would be $300, which is $130 less than the actual total.
(2) Exchanging a $10 bill for a $20 bill keeps the total number of bills the same but increases the total value by $20-$10=$10.
(3) The number of exchanges needed to make up that additional $130 is $130/$10=13.

So 13 $10 bills were exchanged for $20 bills, leaving you with 13 $20 bills and 30-13=17 $10 bills.

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