Answer: 10 cm (choice A)
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Explanation:
One equation we could solve is
x/2.5 = 30/7.5
Note the x/2.5 has us dividing the vertical sides, while 30/7.5 is the same idea for the horizontal sides. The order is large over small. You could do small over large, but make sure you keep both sides consistent.
Solving for x leads to...
x/2.5 = 30/7.5
x*7.5 = 2.5*30
7.5x = 75
x = 75/7.5
x = 10 (choice A)
There are many other possible equations that lead to the same answer. One other possible equation is x/30 = 2.5/7.5
These proportions are possible due to the fact we have similar triangles.
