Banks only accept coins for deposit if they are rolled in

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#1

Banks only accept coins for deposit if they are rolled in

specified amounts. Pennies, for example, are to be in rolls of 50. A Canadian bank has checked the 200 rolls of pennies they have on hand. Only 12 of the rolls contained all Canadian pennies: the rest all had at least one American penny. Altogether in the 200 rolls, about how many American pennies are there?

Answer:

there are 200-12=188 rolls with at least one American penny
since they are in rolls of 50, these rolls could have anywhere between 1 and 50 American pennies in them
so 1(188)=188 pennies at minimum
and 50(188)=9400 pennies at maximum

since we have no info on the distribution of how many pennies are in each, we don’t know much else
if we want to guess the mean, it would be (1/2)(188)+(1/2)(9400)=4794 pennies