Car A began a journey from a point at 9 am, traveling at 30 mph. At 10 am car B started traveling from the same point at 40 mph in the same direction as car A. At what time will car B pass car A?
We can use logic here :
Note that when Car B started......Car A has already traveled 30 miles.......so.....Car B must make up a 30 mile gap
And the difference in speeds is 40 - 30 = 10 mph
So.....Car B makes up a 10 mile gap every hour.....so.....it must take Car B 3 hours to catch Car A, i.e, at 1 PM