Hermione wrote:

Hi BG. How do you set-up the equation? Having a tough time with DRT problems lately.

Hi guys, not sure if this is correct (i think it is ...

)

3 Mins ago, Car X was 0.5 miles ahead.

Now, Car X is 1 mile ahead.

:. Car X Travelled 0.5 miles more than Car Y in 3 mins.

Since [Speed of X] - [ Speed of Y] = ([Distance Covered by X] - [Distance Covered by Y] )x time taken by both X and Y to travel.

-> This relationship can be derived from the first level equation Speed = Dist x Time. If you need to, I can put up the derivation here.

:.[Speed of X] - [Speed of Y] = ((1/2)miles / 3mins) = (1/6) miles per min

Now Car X moves (after time t) to a position 2 miles ahead of Car Y.

That means Car X has moved 1 mile ahead of Car Y.

ie. [Distance Covered by X] - [Distance Covered by Y] = 1 mile

-> [Speed of X] x t - [Speed of Y] x t = 1 mile ----> Distance = Spd x time

Since t is the same for both cars, take out common factor;

-> t x ([Speed of X] - [Speed of Y]) = 1 mile

-> t = 1 / (1/6)

-> t = 6 minutes.

ie . 6 minutes from Now, Car X will be 2 miles ahead of Car Y.