Kali left school and traveled toward her friend's house at an average speed of 40

km/h, Matt left one hour later and traveled in the Opposite direction with an average speed of 50 km/h. Find the number of hours Matt needs to travel before they are 400 km apart.

how can I figure out an equation to solve this problem?

Matt needs to travel 3 hours.

If 40km=1 hour

400km=? But there are two distances

200/40*1=5 hours

Therefore Kali needs to travel 5 hours to be 200 km away from the house.

If 50km=1 hour

200km=?

200/50*1hr=4hrs Therefore Matt needs to travel 4hrs to be 200 km away from the house. But Kali traveled 1hr earlier than Matt. 4hrs-1hr=3hrs

Therefore Matt has to travel for 3 hours to be 400km away from Kali.