Question

Log boats do not go very far. If the wind is helpful, they travel about 4 km in one hour.
How long will they take to go a distance of 10 km?

Answer 1

4:1::10:?
4:1::10:x
4*x=10*1
4x=10
x=10/4
x=2.5

Therefore 2 and an half hour is recquired to  go a distance of 10km

Answer 2

Answer :
           Distance = 10 km
           Speed = 4km / hr
           Time = ?
 we know that ,
     Speed = Distance Traveled / Time Taken
   Substituting the values , we get
         4  = 10 / T  (where T is the Time taken by Boat to Travel distance of 10 km)
  or T = 10 /4
    or T = 2.5 hours

Hope this helps you!!