How long will it take before they are 500 kilometers apart?

Question

A train leaves Little Rock, Arkansas, and travels north at 60 kilometers per hour. Another train leaves at the same time and travels south at 65 kilometers per hour. How long will it take before they are 500 kilometers apart?

Answer 1

Let N=distance traveled by northbound train

S=distance traveled by southbound train

N+S=500km

N=60km/hr X t(in hrs)

S=65km/hr X t(hrs)

This gives the equation: 60t + 65t = 500, with t being the same time. This can be re-written and solved by:

t(60+65)=500

125t=500

t=4hrs

Hope this helps!