It took a crew 6 h 24 min to row 24 km upstream and back again. if the rate of flow of the stream was 2 km/h, what was the rowing rate of the crew in still water.

let the rowing rate in still water be v km/hr

let stream flow rate be u km/hr

upstrean speed = v-u

downstream speed = v+u

total time = upstream time + downstream time

[6+(24/60)]= 24/(v-u) +24/(v+u)

6.4 = 48v/(v2-u2)

u=2 km/hr

2(v2-22)=15v

2v2-15v-8=0

2v2-16v+v-8=0

2v(v-8)+1(v-8)=0

v=8 km/hr