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James took a trip of 2400km ,travelling part by bus and part by plane. The average speed of the bus was 60km/h and the speed of the plane was 700km/h. If the total journey took 8hrs , how many kilometres did he travel by plane ?

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Answer:

2100 km

Explanation:

If the entire trip was 2400 km, then we can note that x km was flown by plane, and 2400 - x km by bus

The whole trip took 8 hours and we know that t = s/v:


t(by \: plane) = (x)/(700)


t(by \: bus) = (2400 - x)/(60)

Now we can form an equation:


(x)/(700) + (2400 - x)/(60) = 8


(60x + 1680000 - 700x)/(42000) = 8


( - 640x + 1680000)/(42000) = 8

Use the property of the proportion:

-640x + 1680000 = 336000

-640x = 336000 - 1680000

-640 x = -1344000 / : (-640)

x = 2100

Since we've noted that x is a path flew by the plane, we have the answer already

User Malte Schwerhoff
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