A train leaves Little Rock Arkansas and travels north at 80

A train leaves Little Rock, Arkansas, and travels north at 80 kilometers per hour. Another train leaves a same time and travels south at 80 kilometers per hour. How long will it take before they are 320 kilometers apart?

Solution

the first train is going towards north with a speed of 80 kilometer per hour

the second train starts at same time to the south with a speed of 80 kilometer per hour

so in a hour 1st train will travel 80 km and 2nd train will travel 80 km

so the distance is 160 km between the trains

so in the 2nd hour 1st train travels 160 km and 2nd train travels 160km

so at t = 2hours

so it will take 2hr