A boat moves upstream at the rate of 1 km in 30 minutes and down stream 1 km in 12 minutes. Then the speed of the current is :  Choices
A) 1.5 kmph	B) 2 kmph	C) 3 kmph	D) 2.5 kmph	E) 3.5 kmph

Rationale: "rate upstream = ( 1 / 30 * 60 ) = 2 kmph rate down stream = 1 / 12 * 60 = 5 kmph rate of the current = ½ ( 5 - 2 ) = 1.5 kmph answer : a"
Answer: A