SOLUTION: a certain journey took 40 min to complete. if half of the distance was travelled at an average speed of 100 km/h and the other half at an average speed of 60 km/h, what was the len

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Question 877648: a certain journey took 40 min to complete. if half of the distance was travelled at an average speed of 100 km/h and the other half at an average speed of 60 km/h, what was the length of the journey? i tried 180 km/h divided by 2 and then i got lost
Found 2 solutions by josgarithmetic, MathTherapy:
Answer by josgarithmetic(39617)   (Show Source): You can put this solution on YOUR website!
RT=D rate, time, distance.

Distance is unknown.
Let d = journey distance.
and using x and y as the times for first half and second half of the journey distance. ALSO, , since we could or should keep in units of time as hours.



, from the R, T, D reationships.
-
, simplified form of the given time sum.
-
Solve the system for x and y:
---------------------
AND
---------------------

When you know x and y, which are in HOURS, you can then find the journey's distance.
Answer by MathTherapy(10552)   (Show Source): You can put this solution on YOUR website!

a certain journey took 40 min to complete. if half of the distance was travelled at an average speed of 100 km/h and the other half at an average speed of 60 km/h, what was the length of the journey? i tried 180 km/h divided by 2 and then i got lost


Let distance of entire journey be D

Then half of journey = , or 

Then time taken on 1st half of journey = , or , or 

Time taken on second half of journey = , or , or 

Since time taken on entire journey = 40 mins, or , or  hour, then we get:  

3D + 5D = 240 ------- Multiplying by LCD, 600

8D = 240 

Distance, or , or  km

You can do the check!! 



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