A boat can move upstream at 15 kmph and downstream at 35 kmph, then the speed of the current is?
Pick one:  A) 5  B) 6  C) 10  D) 8  E) 9
US = 15   DS = 35   M = (35 - 15)/2= 
<gadget id="calculator">(35 - 15)/2</gadget>
<output>10</output>
10   Answer: 10
<result>C</result>
A boat can move upstream at 15 kmph and downstream at 35 kmph, then the speed of the current is?