The important formula to this problem is 
or 
Now, the speed of the car is 70 km/h, and the speed of the truck is 50 km/h. It will take the two vehicles the same amount of time to meet since they both left at the same time. So, since distance equals rate times time, and t = time:
the distance of the car = 70t
the distance of the truck = 50t
Because they both left in opposite directions, and the towns are 420 kilometers apart, the equation for this would be
We now solve the equation.
It will take the vehicles 3 and a half hours to meet. Since we're looking for the time, 3 and a half hours from 10:00 AM is 1:30 PM.
So, the car and the truck will pass each other at 1:30 PM.
Now, the speed of the car is 70 km/h, and the speed of the truck is 50 km/h. It will take the two vehicles the same amount of time to meet since they both left at the same time. So, since distance equals rate times time, and t = time:
the distance of the car = 70t
the distance of the truck = 50t
Because they both left in opposite directions, and the towns are 420 kilometers apart, the equation for this would be
We now solve the equation.
It will take the vehicles 3 and a half hours to meet. Since we're looking for the time, 3 and a half hours from 10:00 AM is 1:30 PM.
So, the car and the truck will pass each other at 1:30 PM.