Banknotes 17573

The eldest sister saved CZK 7,800 in the bank. She brought this amount only in 100CZK and 200CZK banknotes. The total number of these banknotes was 50. How many banknotes of both values ​​were there?

Correct answer:

a =  22
b =  28

Step-by-step explanation:


7800 = 100a + 200b
a+b=50

7800 = 100·a + 200·b
a+b=50

100a+200b = 7800
a+b = 50

Row 2 - 1/100 · Row 1 → Row 2
100a+200b = 7800
-b = -28


b = -28/-1 = 28
a = 7800-200b/100 = 7800-200 · 28/100 = 22

a = 22
b = 28

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