Question
The average mass of a group of pupils is 39 kg. If one more pupil who weighs 69 kg joins the group, the new average mass of the group will become 49 kg. Find the total number of pupils in the group.
3 m

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The average mass of a group of pupils is 39 kg. If one more pupil who weighs 69 kg joins the group, the new average mass of the group will become 49 kg. Find the total number of pupils in the group.