Compare MPG average calculation
 

Question: I've entered 3 mileages in the database
50.4
54.3
55.9

By my calculation this should average out to 53.53 mpg
the datbase comes up with 52 mpg

What's up with that?

Re: Compare MPG average calculation
 

Trying adding the miles for all three tanks and dividing by the gallons for all three tanks. That will give you the real average.

True Avg MPG = (D1 + D2 + D3) / (G1 + G2 + G3)

Note this is different than what you calculated:

Fake Avg MPG = ((D1 / G1) + (D2 / G2) + (D3 / G3)) / 3

-dan

Re: Compare MPG average calculation
 

That's correct Dan, thanks.

If you eat 1 hotdog in a year, then 1 hotdog in a month, then 1 hotdog in a day, how many hotdogs do you average per day? (Hint…it's not 1)

Re: Compare MPG average calculation
 

Can't figure it out with the information provided:
How many days in a year? (365, 365.25, 366, or ?)
How many days in a year? (28, 29, 30, 31, or some average of these numbers)?

Re: Compare MPG average calculation
 

The second line should be How many days in a MONTH?

Re: Compare MPG average calculation
 

Highest average scenario (365 days for the year, then use February for 28, then have the last one on March 1st) comes out to 3 hot dogs in 394 days, or 0.00761421320 hot dogs per day.

Lowest average scenario (Leap year, a month with 31 days, then the final day) comes out to 3 hot dogs in 398 days, or 0.00753768844 hot dogs per day.

For those of you keeping score at home, that's a variance in average of 0.00007652479 hot dogs per day. I'm thinking the difference only works out to a couple poppy seeds on the bun.

("Why?" I hear you ask. I don't know, probably for the same reason a group of us sat around in college in the '80's and figured out the explosive power of a photon torpedo launched from the Enterprise and determined it would be enough energy to blow a battleship to the moon.)

Re: Compare MPG average calculation
 

You can not take an average of averages. Clearly the tank in which you got 50.4 mpg had more miles than the other tanks so it is weighted heaver by the database, as it should be.