Question

Two cars started moving in opposite directions from the same point at the same moment of time. If the speed of one car is 50 mph, and the other car goes at a speed of 60 mph, how soon the distance between them will become 1320 miles?

Answer 1

<---------------------------||----------------------------------------->

           A                                         B

          50 mph                               60 mph

so let's recall that d = rt, distance = rate * time.

both cars start out at the same time, say "t" hours.

after "t" hours car A has covered say "d" miles, since there's a total of 1320, then car B must surely had covered the slack, or 1320 - d.

$\bf \begin{array}{lcccl} &\stackrel{miles}{distance}&\stackrel{mph}{rate}&\stackrel{hours}{time}\\ \cline{2-4}&\\ A&d&50&t\\ B&1320-d&60&t \end{array}\qquad \implies \begin{cases} ~\hfill \boxed{d}=50t\\ 1320-d=60t \end{cases} \\\\\\ 1320-\boxed{50t}=60t\implies 1320=110t\implies \cfrac{1320}{110}=t\implies 12=t$