[Mailbag] What Do You Do with the Ideas You Used to Call “Mistakes”

Guillaume ParĂ©, in the very interesting comments of my last post where I
urged us to reconsider mistakes: I do agree with what is written, but I am
still w...
1 week ago
Answer: 120 mph.
ReplyDeleteLet t be the time in hours for Sue to reach the halfway point. The distance from San Francisco to the halfway point is 40t miles, so the total distance is 80t miles.
If Sue averages 60 mph during the entire trip, then the total time is 80t/60 = 4t/3 hours. Since she used t hours to reach the halfway point, she has only t/3 hours remaining to complete the trip, and she must maintain an average speed of 40/(t/3) = 120 mph.