In the first week of July, a record 1100 people went to the local swimming pool. In the second week, 125 fewer people went to the pool than in the first week. In the third week, 130 more people went to the pool than in the second week. In the fourth week, 280 fewer people went to the pool than in the third week. What is the percent decrease in the number of people who went to the pool over these four weeks?

In July:
First week:
Number of people went to the local swimming pool =1040
Second week:
110 fewer people went to the pool than in the first week
so,
Number of people went to the local swimming pool =1040-110
=930
Third week:
130 more people went to the pool than in the second week
so,
Number of people went to the local swimming pool =930+130
=1060
Fourth week:
228 fewer people went to the pool than in the third week
so,
Number of people went to the local swimming pool =1060-228
=832
Decrease in number of people over four week= number of people in first week - number of people in fourth week
Decrease in number of people over four week=1040-832
=208
now, we can find percentage
Percentage is

=20%Answer

Are you trying to figure out the volume?