4 swimmers swam 100 meters each.
You know the total time all 4 swimmers took to complete the race.
You know the individual times for 3 of the 4 swimmers.
Add the three individual times, and subtract the sum from the total time.
That will give you the time of the 4th swimmer.
First, you need to add 52.58 sec + 59.19 sec + 50.73 sec.
52.58 sec + 59.19 sec + 50.73 sec = 162.5 sec
Now we convert this time into minutes and seconds.
60 seconds = 1 minute
120 seconds = 2 minutes
180 seconds = 3 minutes
The sum we have is 162.5 seconds, so it is between 2 and 3 minutes.
2 minutes = 120 sec, so subtract 120 sec from 162.5 sec.
162.5 seconds - 120 seconds = 42.5 seconds
The sum, 162.5 sec = 2 minutes 42.5 sec.
Now we have the sum we need, 2 minutes, 42.5 sec.
We need to subtract this sum from 3 minutes 29.35 seconds.
3 min 29.35 sec
- 2 min 42.5 sec
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Since we can't subtract 42.5 from 29.35, we borrow 1 minute from the 3 minutes. 1 min = 60 sec, so we borrow 1 min from 3 min, and we add 60 sec to 29.35 sec.
2 min 89.35 sec
- 2 min 42.5 sec
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0 min 46.85 sec
The difference is 46.85 sec.
Answer: the 4th swimmer swam in 46.85 seconds.