A boy rides his bicycle 10 km at an average sped of 12 km/hr and again travels 12 km at an average speed of 10 km/hr. His average speed for the entire trip is approximately.
Select
A) 10.2 kmph	B) 10.4 kmph	C) 10.8 kmph	D) 11.8 kmph	E) None
Sol.   Total distance travelled = (10+12) km/hr = 22 km/hr.   total time taken = [10/12 + 12/10] hrs = 61/30 hrs   ∴ Average speed = [22*30/61] km/hr = 10.8 km/hr.   Answer 10.8 kmph
<result>C</result>
A boy rides his bicycle 10 km at an average sped of 12 km/hr and again travels 12 km at an average speed of 10 km/hr. His average speed for the entire trip is approximately.