I drove to the beach at a rate of $40$ miles per hour. If I had driven at a rate of $55$ miles per hour instead, then I would have arrived $25$ minutes earlier. How many miles did I drive?
Distance = rate X time
the distance is the same for both speeds....so equate them
40 mi/hr * t = 55 mi/hr * (t - .41667) <==== 25 minutes is .41667 hr
-15t = -22.9167
t =1.53 hr
at 40 mi / hr the distance is then 40 mi/hr * 1.53 hr = 61.11 miles