Using proportions, it is found that she will need 85 yards of fabric to make 34 costumes.
A proportion is a fraction of a total amount, and the measures are related using a rule of three. Due to this, relations between variables, either direct or inverse proportional, can be built to find the desired measures in the problem.
For 1 costume, she needs 2.5 yards of fabric. Hence the amount that she needs for 34 costumes is given as follows:
34 x 2.5 = 85 yards.
She will need 85 yards of fabric to make 34 costumes.
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