Question

Sarah rides her horse for 2 1/6 hrs with a constant speed of 6 km/hr and then for another 2 hours and 5 minutes with a constant speed of 12 km/hr what is her average speed for the total trip?

Answer 1

We know that
speed=distance/time

1) Sarah rides her horse for 2 1/6 hrs with a constant speed of 6 km/hr
time=2 1/6 hrs----> 13/6 hrs
speed=6 km/h
distance=speed*time----> 6*(13/6)---> 13 km

2)for another 2 hours and 5 minutes with a constant speed of 12 km/hr
time=2hrs+5 minutes----> 2+(5/60)--> 125/60 hrs
speed=12 km/hrs
distance=speed*time----> 12*(125/60)---> 25 km

3) find the average speed for the total trip
total distance=13 km+25 km----> 38 km
total time=(13/6)+(125/60)----> (10*13+125)/60----> 4.25 hours
speed=38/4.25----> 8.94 km/hrs

the answer is
8.94 km/hrs