Area of Triangle ABC is 800cm2 . AD is a median, E is the mid point of AD. If F is the mid point of AB then find that area of Triangle AEF.


Given   ABC is a triangle and D is the midpoint of BC. Fand E are the midpoints of AB and AD respectively.

Mid point theorem states that the line joining the midpoints of two sides of a triangle is parallel to third side and equals to half of the length of third side.
F and E are the midpoints of AB and AD respectively .Hence FEBD   and FE=12BD

Now as we know that median divides the triangle into two triangles of equal areaareaABD = areaADC =12 area ABCHence areaABD = 12×800 cm2=400 cm2Now in AFE  and ABD,AFE =ABD (corresponding angles as FEBD and AB is a transversal)AEF=ADB (corresponding angles as FEBD and AD is a transversal)FAE =BAD(common)Hence by AAA similarity AFE~ABDareaAFEareaABD =(FE)2(BD)2=(12BD)2(BD)2=14Hence areaAFE = 14area ABD =14×400 cm2=100 cm2

 

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Area of Triangle ABC = 800 cm2

In Triangle ABC

AD is the median

therefore, area of triangle ADB = 1/2 ar(ABC)

In Triangle ADB

E is the midpont of AD

therefore ar(AEB)= 1/2 ar(ADB)

or ar(AEB)= 1/2 * 1/2 ar (ABC)

and F is the midpoint of AB

therefore ar(AEF) = 1/2 ar(AEB)

or ar(AEF) = 1/2 * 1/2 * 1/2 ar(ABC)

ar(AEF) = 1/8 * ar(ABC)

ar(AEF) = 1/8 * 800

ar(AEF) = 100 cm2

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