Question
The average mass of a group of boys is 42 kg. If one more boy who weighs 72 kg joins the group, the new average mass of the group will become 47 kg. Find the total number of boys in the group.
3 m

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The average mass of a group of boys is 42 kg. If one more boy who weighs 72 kg joins the group, the new average mass of the group will become 47 kg. Find the total number of boys in the group.