Eric took 2 hours to travel 3/5 of a journey. He completed the remaining 84 km in 1 hour. What was Eric's average speed for the whole journey?
Let the total distance of the journey==D
1 - 3/5D ==2/5D -this equals the remaining 84 km
2/5D == 84 Cross multiply
2D ==84 x 5 ==420, solve for D
D ==420 / 2==210 km - total distance of his journey.
Average speed ==Total distance / total time
== 210 / 3 ==70 km/hour -his average speed for the entire trip.