<PRE><B>Question 1101416</B>
Juan roller skates for 10 minutes with a  constant speed of 13 km/h and then for
 another 1 hour with a constant speed of  17 km/h.
 What is his average speed for  the total trip?
:
We want both the times in hrs; {{{10/60}}} = {{{1/6}}} or .167 hrs
:
Find the total distance traveled dist = speed * time
13 * {{{1/6}}} = {{{13/6}}} = 2.167km
17 * 1 = 17 km 
total distance 19.167 km
:
Average speed = total dist/total time
total time = 1.167 hrs
{{{19.167/1.167}}} = 16.4 km/hr is the average speed </PRE>