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The official monopoly rules say:

In order to lift the mortgage, the owner must pay the Bank the amount of the mortgage plus 10% interest

However, the utilities have a mortgage value of $75, and 10% of $75 is $7.5. As far as I know, there are no coins or any way to pay less than a dollar to the bank. What would you do in this scenario? Round up? down?

  • There is one more property that will have a mortgage value that needs 0.5 rounding, Park Place/Park Lane (UK) has a mortgage value of 175. This and the utilities are the only three property with a mortgage value that is not even tens. – Andrew Jan 19 '18 at 5:25
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There is no official rule to address this question, so you and your play group must decide how to handle it.

Note that the same question applies in the case of landing on the Income Tax square and choosing to pay 10% of your worth.

A common thing that would make sense is to follow the same rules of rounding that is taught in most basic math... 1/2 and higher means round up, lower than 1/2 means round down. So 7.5 would round up to 8.

But if your group decides on either always rounding up, or always rounding down, that would be equally legitimate.

However, even if you want to use mathematical rounding, there are actually different conventions for handling rounding 1/2... all conventions agree that less than 1/2 means round down, while more than 1/2 means round up. But for 1/2 exactly, there are multiple options.

Because Monopoly is a game designed to simulate handling money, involving banking and such, it might make the most sense to use what is called "Banker's Rounding", which is also known as "Round to even". This means that 7.5 would become 8, but 10.5 would become 10. In other words, when dealing with 1/2, round to whichever direction would leave you with an even number.

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    One quibble - the real point of bankers' rounding is to eliminate a systemic upwards bias when both parties will engage in a large number of transactions, over time, that might round - such as interest transactions between a bank and its customers. For the same reason, it is (or at least should be) used by scientists when collecting data that will be analyzed statistically. For single transactions, such as in Monopoly, there is no overwhelming reason to adopt bankers' rounding; just make a house rule and stick to it. – Forget I was ever here Sep 18 '17 at 19:47
  • @ForgetIwaseverhere While that is true, there is no compelling reason to not use banker's rounding as the system. Though to be honest away from zero or banker's, both will round up for the three properties that are effected. The only possible round down comes in an edge case of paying percentage tax. – Andrew Jan 19 '18 at 5:27
  • @Andrew: Exactly - there aren't enough rounding transactions taking place in any (one) game for such a small statistical phenomenon to achieve significance. Hence: "Just make a house rule and stick to it." – Forget I was ever here Jan 19 '18 at 5:30
  • It's a 10% chance when paying tax, your total worth must end in $5 to end up needing to round with 0.5 rounding on the tax, with the rarity of landing on a given space, coupled with the rarity of having that dollar value, deciding to pay 10% (usually only worth it in the early game or if you're losing already) the rounding system really isn't going to matter much. – Andrew Jan 19 '18 at 5:33

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