A boat moves upstream at the rate of 1 km in 20 minutes and down stream 1 km in 9 minutes. Then the speed of the current is :	Select: A) 1 kmph B) 2 kmph C) 3 kmph D) 2.5 kmph E) 1.85 kmph

Rationale: "rate upstream = ( 1 / 20 * 60 ) = 3 kmph rate dowm stream = 1 / 9 * 60 = 6.7 kmph rate of the current = ½ ( 6.7 - 3 ) = 1.85 kmph answer : e"
Answer: E