A ship sails out to a mark at the rate of 15 kmph. and sails back at the rate of 10 kmph. The average rate of sailing is ? Choose the correct choice from the following answers.
A) 5 km/hr B) 12 km/hr C) 12.5 km/hr D) 25 km/hr E) None
Answer   Average = ( 2uv / u +v ) km/hr   = ( 2 x 15 x 10 ) / (15 +10 ) km/hr.   = 12 km/hr.   Correct Option: 12 km/hr
<result>B</result>
A ship sails out to a mark at the rate of 15 kmph. and sails back at the rate of 10 kmph. The average rate of sailing is ?