January 2008 SAT Hard Math Question HELP #18

JohnTee
Sat, 27 Jul 2013 09:23:00 +0000

^ Although you got the right answer, your formula makes no sense because it is badly explained. Let me show you the formula that you told WorkOverTalent.

muhammad9211:
Avg speed = (total distance) / (total time)

This is what WorkOverTalent will think…

Ok, speed = distance / time, seems easy enough.
Let me just calculate the total distance, oh 20 miles, not too bad.

Now, let me calculate the total time. Ok if you are going 10 miles driving 20mph… easy, 30 minutes, ok now 10 miles driving 40 mph… 15 minutes, even easier. 30 + 15 = 45 minutes.

Ok now that I found the total minutes and total distance, let me plug them in.
Avg speed = total distance / total time
Avg speed = 20 miles / 45 minutes
Ok, Avg speed = 0.4 mph

Right, now that I got the answer let me just… oh wait it’s not on here. Dang, should’ve used JohnTee’s formula.

Now do you understand what I’m trying to say?