SOLUTION: a man completes 30 km of a journey at the speed of 6 km/hr and the remaining 40 kms of the journey in 5 hrs.what is the average speed for the whole journey? a.7 km/hr b.5 9/11 km

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Question 880184: a man completes 30 km of a journey at the speed of 6 km/hr and the remaining 40 kms of the journey in 5 hrs.what is the average speed for the whole journey?
a.7 km/hr
b.5 9/11 km/hr
c.8 km/hr
d.7 1/2 km/hr
Answer by Edwin McCravy(20060)   (Show Source): You can put this solution on YOUR website!

Average speed = 

We find the total DISTANCE traveled this way:

  

Since we are give both DISTANCES, we just add them

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

------------------

We find the total TIME traveled this way:

  

We are NOT given the TIME for the first part of the journey,
So we must use TIME =  to find the TIME for
the first part of the journey.

TIME for first part of journey =  = 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 =  =  = 7 km/hr

Edwin
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