need help with this QR question

[issa]

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Shot at 2007-08-08

the answer is 50. how did they get 50?

 

[Jerryski]

I think this ? is fairly simple and you might be reading into it a bit to much.

He can go 5mph with no current, but there is a 3mph current so his rate is 2mph. He goes 1 mile upstream > d= r*t (1=2*X) X =1/2 hour or 30 minutes. He then floats down stream 1 mile at 3mph. 1=3*t which take 1/3 hour or 20 minutes. Now all you need to do is add them up.

30+20=50.

Best of luck.

 

[Flipper405]

This is fairly straightforward actually. If he can row 5 mph and he rows against an upstream current of 3 mph, he is effectively moving at 2 mph. 2 mph for 1 mile = 1/2 hour or 30 minutes.
When he floats back down a mile, he is traveling at the speed of the current which is 3 mph; 3 mph for 1 mile = 1/3 hour or 20 minutes.
30+20 = 50 minutes.

Good luck