1

I'm confused about averages.

Say a person uses 20 cans of paint, in 5 days. That would that they use 4 cans of paint per day on average

But if a person uses 20 cans of paint in 0.8 days (current day), does that mean they use 25 cans of paint per day on average?

How does that work, since they have only used 20 cans of paint up to that point in the day?

Community
  • 1
Newbie101
  • 167
  • 2
    As you are noticing, it's one thing to interpolate values between known data points and quite another to extrapolate data out of the experimental range. That $25$ might be absurd...possibly the person actually intends to sleep for the remaining $.2$ of a day. To extrapolate data you need to model the situation...you can't reliably do it from the numbers alone. – lulu Sep 20 '19 at 23:17
  • Average = (Total used)/(total days). If total days is a fraction and less than 1 it doesn't matter. It is presumed if the continue using paint at that rate it will be $25$ cans in that day. – fleablood Sep 20 '19 at 23:17
  • yes, you are correct. By saying "uses 20 cans of paint in 0.8 days", we think of that as "using 1 can of paint in 0.04 days" so every 0.04 days, 1 can of paint gets used. That's how averaging works: we have some sort of total amount and total time, and we divide to find the ratio ASSUMING UNIFORMITY. – D.R. Sep 20 '19 at 23:17
  • Could you identify what confuses you? Is it that an average is larger than a total? Consider this. We measure how how many cans of paint you used in 40 weeks and it is $800$ cans. So we figure the average is $20$ cans a week on average. Then we figure that is $1040$ cans a year. Would you feel comfortable saying that the person uses $1040$ cans a year on average? Is this the same, or different than you $20$ cans in $.8$ days? Why or why not? – fleablood Sep 20 '19 at 23:28
  • Please try to make the titles of your questions more informative. For example, Why does $a<b$ imply $a+c<b+c$? is much more useful for other users than A question about inequality. From How can I ask a good question?: Make your title as descriptive as possible. In many cases one can actually phrase the title as the question, at least in such a way so as to be comprehensible to an expert reader. You can find more tips for choosing a good title here. – Shaun Sep 21 '19 at 00:16

0 Answers0