A boat with speed 15 km/hr in standing water goes 30 km downstream and returns in a total of 4.5 hours. What is the speed of current?  Choose the correct answer
A) 8kmph	B) 6kmph	C) 4kmph	D) 5 kmph	E) 1kmph
Explanation:   Speed of the boat in still water: 15 km/hr   Speed of boat downstream: (15+x)km/hr where x is speed of the current.   The boat travels 30 km downstream and then 30 km upstream and takes 9/2 hours.   Total time= Time taken to travel downstream + Time taken to travel upstream   =&gt; 4/5= (30/(15+x))+(30/(15-x))   =&gt;x= 5   ANSWER:5 kmph
<result>D</result>
A boat with speed 15 km/hr in standing water goes 30 km downstream and returns in a total of 4.5 hours. What is the speed of current?