We know the area of a triangle is B*H/2. For Triangle ABC, the area is 75. So the equation formed is:
15*h/2 = 75
15*h = 150
h = 10.
Now we know the height for the bigger triangle is 10. Since the scale factor from 15 --> 3 is 5, the height for triangle EFG is 2 because 10 divided by 5 is 2. Since we now know the height of the triangle is 2 and the base is 3, we can form the equation:
3*2/2 = Area
6/2 = Area
3 = Area
We know the area is 3. The key thing was we didn't divide triangle ABC with 5 because the area would not be the same. We must use the equation and from this we will get the correct area.
