The weight of a person was entered incorrectly as 83 kg instead of 63 kg. As a result, the average weight of a group of people increased by 500 gm. What is the total number of people in the group?

40

Change in avg. weight of group is 500 gm which is 0.5 kg

Change in total weight of group is 20 kg

So, change in sum = number x change in avg.

Number of people in group = 40