Question

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 ?

Answer 1

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