Question 325948
You are driving a car at 45 mph. Your friend is driving his car at 47 mph and leaves 2 hours after you. The two of you follow the same route in the same direction.  How long until your friend catches up with you?
..
You are driving at 45 mph.
let the friend meet you after he has traveled x miles
speed = 47mph
the time taken by your friend to travel x miles  x/47
..
In 2 hours you have already traveled 90 miles.
During this time you travel x-90 miles 
time taken by you = x-90 / 45.
..
x-90 /45 = x/47
47(x-90)=45x
47x-4230=45x
47x-45x=4230
2x=4230
x=2115 miles
..
Distance when he catches up = 2115 miles
His speed = 47mph.
so time taken = 2115/47
45 hours