Question 920377
distance  = 90 km
 time  = 45 minutes
speed  = distance over time
         = 90/45 
         = 2  km per minute

 speed  = 2 km per minute
it means it can travel 2 km in one minute
 In an hour ( i.e 60 minutes ) it can travel =  2 km *60 
                                              = 120 km
so speed of the boat  = 120 km  per hour
                      =120 kmph