The average weight of a group of friends is 54 kg. When one friend weighing 40 kg left the group, the average weight became 55 kg. Find the initial number of friends in the group.
1
5
2
10
3
15
4
20
The average weight of a group of friends is 54 kg. When one friend weighing 40 kg left the group, the average weight became 55 kg. Find the initial number of friends in the group.