Answer:
a) The trains will be 1520 km apart at 2:40 pm for the cargo train and at 4:40 pm for the passenger train.
b) At that time the cargo train has traveled 560.04 km and the passenger train has traveled 960.12 km.
Step-by-step explanation:
a) First, we need to find the distance traveled by the cargo train in the two hours before the passenger train leaves Chicago:
Now, we can find the time when the trains will be 1520 km apart:
Where 1 is for the cargo train and 2 is for the passenger train.
Since we need to calculate the time when the trains are 1520 km apart, t₁ = t₂, so:
![t = \frac{1520 km - 240 km}{120 km/h + 360 km/h} = 2.667h](https://tex.z-dn.net/?f=t%20%3D%20%5Cfrac%7B1520%20km%20-%20240%20km%7D%7B120%20km%2Fh%20%2B%20360%20km%2Fh%7D%20%3D%202.667h)
For the cargo train, it will be 1520 km apart from the passenger train at:
![t_{1} = 12 pm + 2 h + 40 min = 2:40 pm](https://tex.z-dn.net/?f=t_%7B1%7D%20%3D%2012%20pm%20%2B%202%20h%20%2B%2040%20min%20%3D%202%3A40%20pm)
And for a passenger train, it will be 1520 km apart from the cargo train at:
Hence, the trains will be 1520 km apart at 2:40 pm for the cargo train and at 4:40 pm for the passenger train.
b) The distance traveled by both trains is given by:
Therefore, at that time the cargo train has traveled 560.04 km and the passenger train has traveled 960.12 km.
I hope it helps you!