A boat can travel with a speed of 15 km/hr in still water. If the speed of the stream is 3 km/hr, find the time taken by the boat to go 126 km downstream

 a) 4 hours
 b) 6 hours
 c) 7 hours
 d) 9 hours

7 hours. Solution Speed downstream = (15 + 3) km/hr = 18 km/hr. Time taken to travel 126 km downstream = 126/18 = 7 hours.