Remark
Every so often, someone comes up with a variation on the most basic physics formula d = r * t
We will need to think up three formulas to solve this. We may not need all three, but we need them to see how the problem works.
Formula one
Where and when do they meet.
The meet after 6 minutes before Peter finished. Peter finished the course after 24 minutes. Six minutes before that they met. That's 18 after starting they met.
After 18 minutes they completed the course between them
hours to meeting = 18/60 = 0.3 hours
Dave met Peter after a distance of r * t = 70*0.3 = 21 km
Peter had traveled at some speed for 21 minutes = r1 * 0.3 = d1
So the total distance d = is 21 km + r1*0.3 = d
Six minutes later
Peter's Progress
6 minutes later Peter finishes distance D. He does this in 24 minutes.
d = r1 * 24 = r1*24/60 = r1 * 0.4 hours
Dave's Progress
d - 2 = 70 km/hr * 0.4 hr
d - 2 = 28 km
d = 28 + 2 = 30 km
Note this is the total distance that both Peter and Dave travelled.
Question A
How far had Dave gone before he met Peter.
Time = 18 minutes = 0.3 of an hour.
r = 70 km / hour
r = 70 km/hour * 0.3 hour
d = 21 km They met after Dave drove 21 km <<< Answer
Question B
Peter's Rate
d = 30 km
t = 24 minutes = 24/60 = 0.4 hours.
r = 30/0.4 = 75 km/hr. <<< Peter's Speed Answer
