can you find it....-3

Geometry Level 1

A B C D ABCD is a parallelogram. The area of A B C T ABCT is 45 and T T is the midpoint of A D AD . Find the area of triangle A C D ACD .

31 34 25 35 30

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2 solutions

Ashutosh Kumar
Mar 24, 2015

It's a simple problem first take B C = x BC =x , then A T = x 2 AT =\dfrac x2 . And we know that Area of trapezium = Sum of parallel sides × Height 2 \boxed{\text{Area of trapezium}=\dfrac{\text{Sum of parallel sides} \times \text{ Height}}{2}}

Take height as y y and area is given 45 cm 2 \text{ cm}^2 . Therefore x y = 60 xy=60 . And half the area is triangle ACD, hence its area is 60 / 2 = 30. 60/2=30.\square

A B C + A C T = 45 \triangle ABC+\triangle ACT=45

Since T T is the midpoint of A D AD , A D C = 2 × A T C \triangle ADC=2\times \triangle ATC

But A B C = A D C \triangle ABC=\triangle ADC . It follows that A B C = 2 × A T C \triangle ABC=2\times \triangle ATC

\large\therefore 2 × A T C + A T C = 45 2\times \triangle ATC+\triangle ATC=45 . It follows that 3 × A T C = 45 3\times \triangle ATC=45 . From here A T C = 15 \triangle ATC=15 .

Finally,

A D C = 2 × 15 = \triangle ADC=2\times 15= 30 \boxed{\color{#3D99F6}30} answer \boxed{\text{answer}}

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