Can someone please help me get the average miles per gallon for my work round-trip including lunch round-trip? I take the freeway to work which is 16.7 miles. Lunch round-trip 3 to 5 miles. Take surface streets home from work 12.5 miles. Going to work I get anywhere from 56 to 60 miles per gallon, dash reading. Lunch round-trip depending on where I go could be as low as 50 miles per gallon. Going home from work anywhere from 82 to 88 miles per gallon. So a low estimate average: 58 mpg for 16.7 miles 84 mpg for 12.5 miles 50 mpg for 3 miles 58 - 51.86% of the 3 routes 84 - 38.82% of the 3 routes 50 - 9.31% of the 3 routes What would be the average miles per gallon for all 3 routes?
Could you show me how you arrived to that average? A straight average without using distance would be 64.
I would set a trip computer for the day and let the ODO average all the mileage, but I think the math is relatively simple. 58 MPG X 16.7 Mi = 968.6 Mi^2PG (to coin a unit: "Miles squared per gallon") 84 MPG X 12.5 Mi = 1050 Mi^2PG 50 MPG X 3 Mi = 150 Mi^2PG Total = 2168 Mi^2PG 2168 Mi^2PG divided by 32.2 total Mi traveled = 67.35 MPG (notice that Miles cancel and the correct unit MPG is returned.) Pretty Freakin Awesome, what? Someone check my math?
Column 1 0 [tr][th]route[/th][th]mpg[/th][th]miles[/th][th]gallons[/th][th]mpg total[/th][/tr] 1 [tr][td]1[/td][td]58[/td][td]16.7[/td][td]0.29[/td][td]-[/td][/tr] 2 [tr][td]2[/td][td]84[/td][td]12.5[/td][td]0.15[/td][td]-[/td][/tr] 3 [tr][td]3[/td][td]50[/td][td]3.0[/td][td]0.06[/td][td]-[/td][/tr] 4 [tr][td]total[/td][td]-[/td][td]32.2[/td][td]0.50[/td][td]64.8[/td][/tr] Ken@Japan
Quoting-an-embedded-matrix-issues aside... Ok, I understand this methodology, but why does my math differ?
Let's take another example... route-1 50 mpg for 100 miles route-2 100 mpg for 100 miles your math Column 1 0 [tr][th]route[/th][th]mpg[/th][th]miles[/th][th]m^2pg[/th][th]mpg total[/th][/tr] 1 [tr][td]1[/td][td]50[/td][td]100[/td][td]5000[/td][td]-[/td][/tr] 2 [tr][td]2[/td][td]100[/td][td]100[/td][td]10000[/td][td]-[/td][/tr] 3 [tr][td]total[/td][td]-[/td][td]200[/td][td]15000[/td][td]75[/td][/tr] my math Column 1 0 [tr][th]route[/th][th]mpg[/th][th]miles[/th][th]gallons[/th][th]mpg total[/th][/tr] 1 [tr][td]1[/td][td]50[/td][td]100[/td][td]2[/td][td]-[/td][/tr] 2 [tr][td]2[/td][td]100[/td][td]100[/td][td]1[/td][td]-[/td][/tr] 3 [tr][td]total[/td][td]-[/td][td]200[/td][td]3[/td][td]66.7[/td][/tr] I believe my math is correct. Ken@Japan
Your math is the better, elegant, and obvious solution. I'll take my head-scratching offline for now. I sit at your feet.
Is it like saying that since you drive to work at 20mph and drive home at 30mph, you average 25 mph for the trip, but thats not right because you used more time to get to work at 20mph, so your average speed is lower than 50/50? Just like OP uses more gallons at a lower mpg's?
The simple answer is that you can't average averages to get the correct average. (you will not get the correct answer if you average 2 means).
