Question 1139526
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The similarity coefficient "k" is the ratio of "f" to "c"   k = {{{10/5}}} = 2.


Hence, the side "e" is  e = k*b = 2*4 = 8.


Then the perimeter of triangle DEF is  d + e + f = 12 + 8 + 10 = 30 cm.   <U>ANSWER</U>
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Solved.