Alan

I think the expected number of coupons will be 0.6n, where n is the number of visits of the regional manager.

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In that case feel free to use 0/0, but don't expect to pass too many mathematics exams!

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I'm not sure if you really want to know or if you've set it as a puzzle! Either way:

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"Undefined" means there is no value for 0/0 in mathematics.  Expressions that contain or result in 0/0 are not mathematically valid.   The reason is that it can lead to illogical results (you could use it to show that 1 equals 2 for example!).

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This simplifies to 12n² + 5

To evaluate this you need to know the value of n

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This is undefined.

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When looking for the units digit of 3ⁿ, look at the value of mod(n,4).  When this is 0, the units digit is 1, when it is 1 the units digit is 3, when it is 2 the units digit is 9, when it is 3 the units digit is 7.

mod(777,4) = 1, so the units digit of 3⁷⁷⁷ is 3.

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Percentage change = 100*(57 - 28)/57 ≈ 50.9%

In general the percentage change is the difference between the final amount and the initial amount divided by the initial amount and multiplied by 100.

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