What fraction of the total number of pupils in the school are girls

Bài tập về nhà:
1. There are 3 classes in a school. The number of pupils in each of the three classes is the same. The fraction of girls in class 1A is the same as the fraction of boys in class 1C. 1/5 of the total boys in the school are in class 1B. What fraction of the total number of pupils in the school are girls?
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