a man drives 108 km at an average rate. If he had driven 5km/hr. faster, he would have made the trip in 15 hours less time. How fast did he drive?
You know that .
Distance km
Speed km/h
If he had driven km/hr faster, he would have reached in hours less time.
That means... Actual Time taken Time taken while driving km/h faster hours.
Now express as a single fraction:
Now multiply both sides by the denominator, .
Divide throughout by :
Now factorise:
Either (discard) or .
Check: So he was driving at km/h.
Time taken to drive at km/h hours.
Time taken to drive at km/h hours.
Difference in times hours.
at above poster.
I hope that helps.
ILoveMaths07.