The speed at which a man can row a boat in still water is 15 km/hr. If he rows downstream, where the speed of current is 3 km/hr, how many seconds will he take to cover 90 meters? Select.
A) 12  B) 16  C) 17  D) 18  E) 20
The speed of the boat downstream = 15 + 3= 
<gadget id="calculator">15 + 3</gadget>
<output>18</output>
18 km/hr   18 km/hr * 5/18= 5 m/s   The time taken to cover 90 meters = 90/5= 
<gadget id="calculator">90/5</gadget>
<output>18</output>
18 seconds.   The answer is 18.
<result>D</result>
The speed at which a man can row a boat in still water is 15 km/hr. If he rows downstream, where the speed of current is 3 km/hr, how many seconds will he take to cover 90 meters?