Arecent flu epidemic, the number of flu cases increased by 40% each week. there were 3,000 flu cases during the first week of january. how many more people were affected by the flu during the third week of january than during the first week?

In this question it is already given that the number of flu cases increases by 40% each week. The number of flu cases in the first week of January was 3000. Now we have to deduce the number of more people affected by flu during the third week of January.
Percentage of increase in the number of flu cases per week = 40%
Number of people affected by flu during 1st week of January = 3000
Then
Number of people affected by flu during the 2nd week of January = (40/100) * 3000
                                                                                                         = 40 * 30
                                                                                                         = 1200
Then after 2 weeks the number of people affected by flu = (3000 + 1200)
                                                                                           = 4200
The number of people affected by flu during
the 3rd week of January = (40/100) * 4200
                                       = 40 * 42
                                       = 1680
So the total number of people affected by flu during
the 2nd and 3rd week of January = (1200 + 1680)
                                                     = 2880
So from the first week of January to the third week of January total of 2880 more people were affected by flu.
                                                                                                      

This picture .