Aferry departs from a port along the sands river at 10: 00 am. the ferry travels at a speed of 15 mph in still water and returns to port at 2: 00 pm. if the ferry trip upstream takes twice as long as its return trip downstream, what is the speed of the river’s current

Speed of river's current = 5 mph

Step-by-step explanation:

Let 'd' be the distance covered  

 Let x be the speed of the rivers current

Speed upstream = 15-x

speed downstream = 15+x

Time = distance / speed

time upstream =

time downstream =

the ferry trip upstream takes twice as long as its return trip downstream

=

divide both sides by d

=

cross multiply

Add 2x on both sideds

subtract 15 from both sides and divide by 3

x=5

Speed of river's current = 5 mph