Question 30730
upstream distance = 240 miles
upstream time = 10 hours
upstream speed = ?
(applying the formula.. speed = distance / time) 
= 240/10
= 24 miles/hour 

down stream distance = 240 miles
down stream time = 8 hours
down stream speed = ?
(applying the formula ..speed = distance / time) 
= 240/8
= 30 miles / hour 

Now speed of boat in still water = (downstream speed + upstream speed)/2 
= (30 + 24)/2 
= 54 / 2 
= 27 miles /hour 
 
Now speed of current = (downstream speed - upstream speed)/2 
= (30 - 24) /2 
= 6/2 
= 3 miles /hour 

hope this will help you 

Please feel free to revert back for any further queries.