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I am working on this question:

An assembly operation for a computer circuit board consists of four operations that can be performed in any order.

a) In how many ways can the assembly operation be performed?

b) One of the operations involves soldering wire to a microchip. If all possible assembly orderings are equally likely, what is the probability that the soldering comes first or second?

In part a, I just use $4! = 24$

In part b, I can't get it, I'm a little confused about "comes first or second". Should I get the individual probabilities and just add them?

My answer in part b is $\frac{6}{64} + \frac{6}{64}$. Is that correct?

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    Its rather unfortunate that you ask us 5 questions in a row in an hour or so. Please don't try to get your home work issues sorted out here.2012-01-22

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Yes, you should get the individual probabilities and add them.

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    Some people would try to calculate the probability of soldering being second by adding up the cases according to which comes first, then soldering second. But that is completely unnecessary.2012-08-03
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Answer to part b) of your question is 0.5