Two cars started from the same point, at 5 am, traveling in opposite directions at 40 and 50 mph respectively. At what time will they be 450 miles...

Let us call the cars A and
B.

Car A travels at S(A) = 40
mph

Car B travels at S(B) = 50
mph

We need to know the time T such that the
distance between the cars is 450 m.

1.Let us assume that
the distance car A travels is DA

and the distance that car
B travels is DB

==> D = DA + DB =
450..........(1)

Now let us calculate the
time.

T = D/S

==> T =
DA/ 40

==> T=
DB/50

==> DA/40 =
DB/50

==> DA/4 = DB/
5

But DA + DB = 450

==>
(450-DB) /4 = DB/5

==> (450-DB)*5 =
4DB

==> 2250 - 5DB =
4DB

==> 9DB =
2250

==> DB = 250
miles

==> T = 250/50 = 5
hours,

Then the cars will be 450
miles apart after 5 hours.