Machine 18483

Coins worth 20 cents and 50 cents are thrown into a coffee machine. There are 199 coins in the machine with a total value of € 68. How many are 20-cent coins in the machine?

Correct answer:

a =  105

Step-by-step explanation:


20a+50b = 68·100
a+b = 199

20·a+50·b = 68·100
a+b = 199

20a+50b = 6800
a+b = 199

Row 2 - 1/20 · Row 1 → Row 2
20a+50b = 6800
-1.5b = -141


b = -141/-1.5 = 94
a = 6800-50b/20 = 6800-50 · 94/20 = 105

a = 105
b = 94

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