A boat goes 100 km downstream in 10 hours, and 80 km upstream in 20 hours. The speed of the stream is?  Choose the correct choice from the following answers:	A) 4km/h	B) 3km/h	C) 2km/h	D) (1/2) km/h	E) E)None
100 --- 10 DS = 10   ? ---- 1   80 ---- 20 US = 4   ? ----- 1 S = (10 - 4)/2= 
<gadget id="calculator">(10 - 4)/2</gadget>
<output>3</output>
3 kmph   ANSWER:3km/h
<result>B</result>
A boat goes 100 km downstream in 10 hours, and 80 km upstream in 20 hours. The speed of the stream is?