What do you think?

[JAGG]

Well the question is ambiguous .If you have to pay each time you use the scale, does putting them on and then off count as one time or two? Also if you have to pay everytime you use the scale what's the goal here, what's the object of this quest? To spend the least amount of money possible in your quest, or is the goal to find out which coin is bogus? Anyway I have about 20 more questions because your details are not very clear. But here's my answer. Assumming putting all the coins on the scale counts as a one time use , and taking them all off counts as an additional use, I'd put all the coins on the scale. ( that's one time) Then I'd take them off one at a time, watching the scale for the difference in weights. (For example the first 15 I took off, all weighted 3 ounces each but the 16th one weighted 2 ounces, and the next 4 I took off weighted 3 ounces, I'd set the one that weightes 2 ounces aside) I'd set the different one aside and finished taking the other coins off, that would count as the second use of the scale. So 2 times I'd use the scale. If putting them on and off counts as one time use then I only used the scale once.