Question 972277
The boat's speed downstream is 2.36 +1.22=3.58  all units here m/sec

Upstream is 2.36-1.22=1.14 m/sec

x=time  downstream (% of total)

100-x= time upstream (100-x %)

3.58 x= 1.14 (100-x)
3.58 x=114-1.14x
4.72x=114
x=24.15%  of time downstream

Now convert units.  First is time 139 minutes*0.2415=33.57 minutes spent going downstream
That will mean 105.43 minutes spent going upstream.

Time downstream is 3.58 m/sec*60 sec/min=214.8 m/min
Multiply that by number of minutes and we get 7210.8 m or 7.21 km

Upstream is 1.14 m/sec*60 sec/min = 68.4 m/min
Multiply that by 105.43 minutes and we get 7211.4 m or 7.21 km.  The difference is rounding error.