A boat can move upstream at 30 kmph and downstream at 15 kmph, then the speed of the current is? Pick one.
A) 5  B) 7.5  C) 32.5  D) 9.2  E) 5.8
US = 30   DS = 15   M = (30 - 15)/2= 
<gadget id="calculator">(30 - 15)/2</gadget>
<output>15/2 = around 7.5</output>
7.5   Answer: 7.5
<result>B</result>
A boat can move upstream at 30 kmph and downstream at 15 kmph, then the speed of the current is?