How do I convert per capita to actual numbers?

October 9, 2017 7:40 AM

With all the talk with gun deaths going on, I wanted to figure out in real numbers, how many people die in different countries to guns. The common statistic used is gun deaths per 100,000 people. I know for example if there are 50 deaths in a population of 800,000, you get .0000625. Move the decimal point over 4 places to get a rate of 6.25 per 100,000 people. Using those same numbers, how do you get to 50 deaths, knowing the population is 800,000 with a rate of 6.25? I'm sure this is probably basic algebra, but the answer eludes me!
posted by FireStyle to Society & Culture (4 answers total)

Whatever the "per X people" is, take the total population of the country, divide by X, and then multiply that number by the given rate. That will give you a total # of deaths.
posted by brainmouse at 7:42 AM on October 9, 2017

Response by poster: LOL... I got it literally 2 seconds after I hit post... for those who are wondering:

6.25/100000

.000625*800000

=50

=)
posted by FireStyle at 7:43 AM on October 9, 2017 [1 favorite]

Or

800000/100000 = 8
8*6.25 = 50

Same thing in a different order, but a bit easier to do in your head.
posted by koolkat at 8:53 AM on October 9, 2017 [1 favorite]

Factor-label method! For simple ratios like this, you don't have to memorize which things you want to divide by and which multiply by depending on which specific amount you are looking for. You just set it up so that the units you don't want divide into each other and cancel out, leaving only the units you want behind.

So for your question, you know that in a population of 800,000 people there are 6.25 deaths per 100,000 people (remembering that "per" means "for each," which in mathematical terms means "divided by," or in specifically fractional terms, "over"), and you are looking for a final unit of deaths:

800,000 people | 6.25 deaths               800,000 people | 6.25 deaths
------------------------------------------- = ----------------------------------------------
                                | 100,000 people                                        | 100,000 people

So 800,000*6.25/100,000 or, as noted above, (800,000/100,000)*6.25 to get there a bit quicker in your head.
posted by solotoro at 10:22 AM on October 9, 2017 [2 favorites]