A boat moves upstream at the rate of 1 km in 40 minutes and down stream 1 km in 12 minutes. Then the speed of the current is : Choose the correct choice from the following:
A) 1 kmph
B) 2 kmph
C) 1.75 kmph
D) 2.5 kmph
E) 3.5 kmph
Rate upstream = (1/40 *60)= 
<gadget id="calculator">(1/40 *60)</gadget>
<output>3/2 = around 1.5</output>
1.5 kmph   Rate dowm stream= 1/12 * 60= 
<gadget id="calculator">1/12 * 60</gadget>
<output>5</output>
5 kmph   Rate of the current= ½ (5-1.5) = 1.75 kmph   ANSWER:1.75 kmph
<result>C</result>
A boat moves upstream at the rate of 1 km in 40 minutes and down stream 1 km in 12 minutes. Then the speed of the current is :