The speed of a boat in still water is 12 kmph. What is the speed of the stream if the boat can cover 32 km downstream or 16 km upstream in the same time?  Choose the correct answer.
A) 5 kmph	B) 6 kmph	C) 7 kmph	D) 4 kmph	E) 10 kmph

Rationale: "x = the speed of the stream ( 12 + x ) / ( 12 - x ) = 2 / 1 12 + x = 24 - 2 x 3 x = 12 x = 4 km / hour if the speed of the stream is 4 km / hour , then the ' downstream ' speed of the boat is 12 + 4 = 16 km / hour and the ' upstream ' speed of the boat is 12 - 4 = 8 km / hour . in that way , if the boat traveled for 2 hours , it would travel 2 x 8 = 16 km downstream and 2 x 16 = 32 km / hour upstream . answer : d"
Answer: D