A woman swims downstream 45 km and upstream 15 km taking 3 hours each time, what is the speed of the woman in still water? Choose the correct choice from the following:
A) 10  B) 12  C) 14  D) 16  E) 18
45 --- 3 DS = 15   ? ---- 1   15 ---- 3 US = 5   ? ---- 1 M = ?   M = (15 + 5)/2= 
<gadget id="calculator">(15 + 5)/2</gadget>
<output>10</output>
10   10nswer:10
<result>A</result>
A woman swims downstream 45 km and upstream 15 km taking 3 hours each time, what is the speed of the woman in still water?