# [?] Why does "1 per week" not correctly handled with "1 month"?

Posted 4 years ago
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 I want to use this function to express that the number of event managers acquired is growing 1 per week. If you look at my evaluation result mathematica does what I like to express. growtheventmanager[number_, pertime_] := number / pertime growtheventmanager[1, Quantity[1, "Week"]] Out=1 per week Next I want to calculate the number of event managers after 4 weeks. The calculation is done like expected. Quantity[4, "Week"] * growtheventmanager[1, Quantity[1, "Week"]] Out=4 Next i tried what happens if trust Mathematicas ability to handle Units correctly. Quantity[1, "Month"] * growtheventmanager[1, Quantity[1, "Week"]] Out=365/84 I have no idea what this is all about? Do you have an idea? Answer
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Posted 4 years ago
 This result seems correct to me. Your calculation is basically asking for how many weeks in a month: Quantity[1, "Month"]/Quantity[1, "Week"] Since both of these have a dimension of time, we expect their ratio should be dimensionless. Additionally, we expect that the result should be around 4. More specifically, it should be close to 52/12 since there are 52 weeks in a year and 12 months in a year. Mathematica returns a result that's consistent with all of these. What kind of result were you expecting from the calculation above? There's probably a different way of doing it. Answer
Posted 4 years ago
 Dear Sean,thanks for helping! Quantity[1, "Week"] / Quantity[1, "Day"] evaluates to 7. Why does Quantity[1, "Month"] / Quantity[1, "Week"] not evaluate to 4 with respect to the above. I want to do calculations where I just enter growth like 8 per month or 100 per year and are able to compute the count in a weekly base. Answer
Posted 4 years ago
 There are very clearly 7 days in a week by its definition. There are 12 months in a year. If we said there were 4 weeks in a month, then the unit system would claim that there are 7 * 4 * 12 = 336 days in a year. So we can't do that. I suppose you could create your own Units with different names like "SimplifiedDay", "SimplifiedWeek", "SimplifiedYear". But that might be a fair amount of work and not worth it. Answer