Answer: 122.5
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Explanation:
First thing to do is to find the perimeter of figure B. Add up all the sides and we get: 5+9+9+12 = 14+21 = 35.
The scale factor 7:2 means that if the perimeter of figure A was 7, then the perimeter of figure B would be 2. Or it could be 14 for A and 4 for B. And so on. The idea is that the two perimeters scale up or down together. This allows us to set up the proportion below in which we can solve for x
(perimeter of A)/(perimeter of B) = 7/2
x/35 = 7/2
x*2 = 35*7 .... cross multiply
2x = 245
2x/2 = 245/2 .... divide both sides by 2
x = 122.5
The perimeter of figure A is 122.5
