A boat can move upstream at 15 kmph and downstream at 23 kmph, then the speed of the current is?
Choose the correct choice from the following answers:
A) 5 kmph  B) 7 kmph  C) 8 kmph  D) 9 kmph  E) 4 kmph
US = 15   DS = 23   M = (23 - 15)/2= 
<gadget id="calculator">(23 - 15)/2</gadget>
<output>4</output>
4   Answer:4 kmph
<result>E</result>
A boat can move upstream at 15 kmph and downstream at 23 kmph, then the speed of the current is?