a man swims downstream 28 km and upstream 16 km taking 4 hours each time, what is the speed of the man in still water?  Choose the most appropriate option:
A) 6.5  B) 8.6  C) 7.5  D) 9.2  E) 5.5
<gadget id="calculator">16 / 4</gadget>
<output>4</output>

<gadget id="calculator">28 / 4</gadget>
<output>7</output>

<gadget id="calculator">4 + 7</gadget>
<output>11</output>

<gadget id="calculator">11 / 2</gadget>
<output>11/2 = around 5.5</output>

<result>E</result>
a man swims downstream 28 km and upstream 16 km taking 4 hours each time, what is the speed of the man in still water?
divide(add(divide(16, 4), divide(28, 4)), const_2)
"28 - - - 4 ds = 7 ? - - - - 1 16 - - - - 4 us = 4 ? - - - - 1 m = ? m = ( 7 + 4 ) / 2 = 5.5 answer : e"