effectively he gains 10 m every 2 minutes
but for the last 10 m he does not have to rest 1 minute to reach his goal.
That is, at the end of
2 minutes, he has gone 10 m
4 minutes, he has gone 20 m
...
36 minutes, he has gone 180 m
Since he can swim 20 m per minute, he will reach the 200 m after 37 minutes.
I did this same question last year in a slightly different way
http://www.jiskha.com/display.cgi?id=1420892277
notice the comment at the very end of that post.
a man was trying to swim to a buoy placed at a distance of 200m out in the sea. it took him 1 min to swim 20m. then a wave pushed him back 10m and he rested for about 1min before swimming again. he continued in his way for the rest of their journey. how long would it take the man to swim to the buoy?
1 answer