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.
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 , simplified form of the given time sum.
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Solve the system for x and y:
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 AND 
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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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