a mathz question.
2008-07-19 6:34 pm
There are only coins of 2 different face values in Sandy's purse, each have 5 coins and 7 coins respectively, and the total amount is $39. When Sandy takes out 4 coins each of the 2 face values, the amount left becomes $11. What are the 2 diferent face values?
回答 (1)
2008-07-19 6:43 pm
✔ 最佳答案
Let face value of the 2 kinds of coins be x and y.Therefore, 5x + 7y = 39......................(1)
And (5x+7y) - (4x +4y) = 11
Simplify (2) to x + 3y = 11...................(2)
5 x (2) - (1) we get
5x + 15y - 5x -7y = 55-39 = 16
8y = 16
y=2.
Substitute into (1) 5x + 14 = 39
5x = 25
x=5,
Therefore, the face values are $2 and $5.
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