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Unformatted text preview: 16 Counting (cont.) 16.1 Solving problems by applying basic principles often there are restrictions e.g. third letter must be A or E first digit must not be zero usually best to deal with restrictions first often helpful to use boxes e.g. arrangements of all letters of BLISTER no restriction start with B end with a vowel e.g. 3digit numbers from digits 02468 implied restriction: first cannot be zero another common restriction values must be adjacent e.g. arrangements of 12345 in which 1 and 2 are adjacent another common variation elements in a circle illustrate with ABC in a circle only 2 arrangements generally use one value as a marker arrange others relative to the marker 16.2 The addition or sum rule If one operation can be performed in m ways or a second operation can be performed in n ways, and only one of the operations can be performed , then the number of possible operations is m + n in set terms given sets A and B with A B = ,  A B  =  A  +  B  this rule is often useful with a complement of a restriction...
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 Fall '06
 Carter

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