the speed at which a man can row a boat in still water is 15 kmph . if he rows downstream , where the speed of current is 5 kmph , what time will he take to cover 60 metres ?
"speed of the boat downstream = 15 + 5 = 20 kmph = 20 * 5 / 18 = 50 / 9 m / s hence time taken to cover 60 m = 60 * 9 / 50 = 10.8 seconds . answer : c"
divide(60, multiply(add(15, 5), const_0_2778))