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In triangle ABC, point D belongs to AC with AD:DC=4:3, and point E belongs to BC so that BE:EC = 1:5. If Acde=5, find Abdc, Aabd, and Aabc.

User Ben Gubler
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1 Answer

13 votes
13 votes

In triangles with the same altitude, area is proportional to the base length. Triangles CDE and BDE both have the same altitude (the perpendicular distance from D to BC), so their areas are in the proportion BE:EC = 1:5. Since ACDE = 5 in², ABDE = 1 in². The area of BDC is the total of those:

... ABDC = 6 in²

Likewise, triangles ABD and CBD both have an altitude that is the perpendicular distance from B to AC. Then, ...

... AABD : ACBD = AD : CD = 4:3

Thus AABD = 4/3 × ACBD = 4/3 × 6 in²

... AABD = 8 in²

Of course, AABC is the sum of AABD and ABDC, so is ...

... AABC = 6 in² + 8 in²

... AABC = 14 in²

i hope this helps

User Andres
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