if a car had traveled 20 kmh faster than it actualy did, the trip would have lasted 30 minutes less. If the car went exactly 60km, at what speed did it travel?
Answer is B, given by the following equation:
60/x = 60/x+20 + 0.5 ; backsolving with 40 does it.
Is there a better way to solve this?
quite honestly, comparing for times or speeds is the easiest method in distance-speed-time problems..
if your not very comfortable, another alternatively easy method is substitution..
i tried the substitution technique and nailed the ans in about 45 sec