What is the perimeter formula for a triangle with side lengths a, b, and c?
QUESTION
What is the perimeter formula for a rectangle with length l and width w?
QUESTION
What should you do if one exterior side length is not labeled but can be deduced?
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ANSWER
Use equal/opposite sides or subtraction to find it, then add. In symmetric or composite figures, deduce unlabeled outer sides using properties like congruence or by subtracting known lengths from totals.