Question
The average mass of a group of girls was 36 kg. When a boy, Will, joined the group, the average mass of the group became 31 kg. If Will had a mass of 21 kg, how many girls were there in the group in the end?
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The average mass of a group of girls was 36 kg. When a boy, Will, joined the group, the average mass of the group became 31 kg. If Will had a mass of 21 kg, how many girls were there in the group in the end?