A man can row his boat with the stream at 12 km/h and against the stream in 8 km/h. The man's rate is?
Pick: A) 2 kmph B) 6 kmph C) 7 kmph D) 4 kmph E) 9 kmph

Rationale: explanation : ds = 12 us = 8 s = ? s = ( 12 - 8 ) / 2 = 2 kmph answer : a
Answer: A