Question 759942

A truck heads north at a constant speed of 80 km/h. A car leaves 20 minutes 
later heading north along the same road and travelling at a constant speed of 
90 km/h.
 
Write an equation that could be used to determine how much time in 
hours, t, the car travels until it catches up to the truck. 

**The correct answer is 90t = 80(t+1/3) , but I need help understanding why** 


Let time it takes car to catch up to truck (get to meeting point) be T


Then time it'll take truck to get to meeting point = T + 1/3, since the truck will take a longer time to get to the meeting point as it's traveling at a slower speed


Distance car travels to get to meeting point = 90(T), or 90T


Distance truck travels to get to meeting point = 80(T + 1/3)


Both vehicles would've traveled the same distance, so: {{{highlight_green(90T = 80(T + 1/3))}}}