Question 1107113

Perimeter ABC is 5+6+7 = 18 units.

DE and AB are the corresponding sides of the similar triangles and have a ratio of 3:5 (3/5). 

Thus, the perimeter of  DEF is (3/5)(18) = <b>10.8 units</b>.    

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perimeter(DEF) = DE + EF + DF = (3/5)AB + (3/5)BC + (3/5)AC = (3/5)(AB+BC+AC) = (3/5)(perimeter(ABC))