After 100 new people move into a town, 400 of the original population move out. Every year afterward, the town’s population is halved. After 4 years, the population is 60 people. Before the new people moved in, how many people lived in the town?
How many people were there in the fourth year? ** If the population is halving then at the end of the third year, the population must have been 60 people in the fourth year * 2 = <<60*2=120>>120 people.
How many people were there in the third year? ** In the second year, the population was 120 people in the third year * 2 = <<120*2=240>>240 people.
How many people were there in the first year? ** And in the first year, the population was 240 people in the third year * 2 = <<240*2=480>>480 people.
How many people were there in the first year? ** Additional people moved out in the first year, so accounting for these shows the population was 480 people + 400 people who moved out = <<480+400=880>>880 people.
How many people were there in the first year? ** Then removing the new people shows there were originally 880 people – 100 new people = <<880-100=780>>780 people.
#### 780