Question 880184
<pre>

Average speed = {{{matrix(1,3,Total,DISTANCE,traveled)/matrix(1,3,Total,TIME,traveled)}}}

We find the total DISTANCE traveled this way:

{{{(matrix(9,1,
DISTANCE,traveled, on, the,first, part, of, the, journey))}}}{{{""+""}}}{{{(matrix(9,1,
DISTANCE,traveled, on, the, second, part, of, the,journey))}}} {{{""=""}}} {{{(matrix(7,1,
Total, DISTANCE,traveled, on, the, whole, journey))}}}

Since we are give both DISTANCES, we just add them

30km + 40km = 70km = total DISTANCE traveled on the entire journey

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We find the total TIME traveled this way:

{{{(matrix(9,1,
TIME,traveled, on, the,first, part, of, the, journey))}}}{{{""+""}}}{{{(matrix(9,1,
TIME,traveled, on, the, second, part, of, the,journey))}}} {{{""=""}}} {{{(matrix(7,1,
Total, TIME,traveled, on, the, whole, journey))}}}

We are NOT given the TIME for the first part of the journey,
So we must use TIME = {{{(DISTANCE)/(RATE)}}} to find the TIME for
the first part of the journey.

TIME for first part of journey = {{{30/6}}} = 5 hours

We ARE given the TIME for second part of journey = 5 hours

5hrs + 5hrs = 10hrs = total TIME traveled on the entire journey


Average speed = {{{matrix(1,3,Total,DISTANCE,traveled)/matrix(1,3,Total,TIME,traveled)}}} = {{{70km/(10hrs)}}} = 7 km/hr

Edwin</pre>