Question 898502
A car traveled from A to B in 6 hours. Its average speed for the first three 
hours was 60 mph, and for the last three it was 40 mph. Find the average speed
for the whole trip.
<pre>
We will use:
{{{matrix(1,4,   Average,speed,""="",matrix(1,2,total,distance)/matrix(1,2,total,time))}}}
</pre>
Its average speed for the first three hours was 60 mph
<pre>
{{{matrix(1,9,We,use,distance,""="",rate,"×",time,""="","60×3"=180miles)}}}
</pre>
for the last three it was 40 mph
<pre>
{{{matrix(1,10,Again,we,use,distance,""="",rate,"×",time,""="","40×3"=120miles)}}}
{{{matrix(1,5,total,distance,""="",180+120=300,miles)}}}

{{{matrix(1,5,total,time,""="",3+3=6,hours)}}}

{{{matrix(1,7,   Average,speed,""="",matrix(1,2,total,distance)/matrix(1,2,total,time),""="",300/6=50,mph)}}}

Edwin</pre>