In the above picture, X and Y are midpoints of DC & BC. Area of triangle AXY can be expressed as S times of the area of ABCD. Find S*8. ABCD is a //gm
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Assuming ABCD to be a parallelogram:
-Let U be the midpoint of AB , V the midpoint of AD and O the midpoint of both UX and VY .
-As Y is the midpoint of BC , ABY is 2 1 of ABYV , which is 2 1 of ABCD ., thus ABY is 4 1 of ABCD .
-Similarly as X is the midpoint of AD , ADX is 2 1 of ADXU which is 2 1 of ABCD ., thus ADX is 4 1 of ABCD ..
- CXOY is 4 1 of ABCD . and CXY is 2 1 of this area so CXY is 8 1 of ABCD .
Finally AXY = (1- ( 4 1 + 4 1 + 8 1 )) x ABCD , so S = 8 3
Thus 8 × S =3
AXY =[ 1- (1/4 +1/4 +1/8) ] * ABCD
Let a be the height of ABCD; b be the length CD=AB; ar of ABCD = ab; ar of triangle ADX=ab/4; ar of triangle XCY= ab/8; ar of triangle ABY= ab/4; ar of triangle AXY= Sab=ab-(ab/4)-(ab/8)-(ab/4)=3ab/8; S=3/8;S 8=(3/8) 8=3
If area of //gm is Q, Area of ADX is Q/4. Area of ABY = Q/4. Area of XCY = Q/4. Remaining area = Q-Q/4-Q/4-Q/8=3*Q/8
Area of the given triangle is equal to the area of the parallelogram minus sum of areas of the remaining three triangles. And, two of the triangles share a common base (with the parallelogram) but half the altitude, so their areas are both 1/4 of parallelogram, and the third triangle has both the base and the altitude half of those of parallelogram so its area is 1/8 of that of parallelogram. Therefore, required area = (1-1/4-1/4-1/8)xparallelogram.
Assume the longest side is 4 units and smaller side is 2 units. So area of parallelogram is 8 Sq.units.
X is mid point of larger side, so BX =2, XC=2
Y is mid point of smaller side, so CY=1and ZB=1.
Area of 🔺 ADX =1/2(3
Explained simply:
Axyz = ab bc - ab bc/4 - ab bc/4 - ab bc/8
Axyz = ab bc - (2 ab bc/8 + 2 ab bc/8 - ab bc/8)
Axyz = 3ab*bc/8
Axyz/Aabcd = 3/8
Times 8.... --> 32x 2)=2 Sq.units Similarly Area of 🔺 XCY = 1. Sq unit And area of 🔺 ABZ =2 Sq units
Area of square - area of these 3 triangles give area of 🔺 AXZ . i .e = 8-2-2-1=3 Sq units .
As per given relation, AREA AXY= S (AREA ABCD) 3= S X 8 S= 3/8
So 8s=3
OR
Axyz = ab x bc - ab x bc/4 - ab x bc/4 - ab x bc/8
Axyz = ab x bc - (2 x ab x bc/8 + 2 x ab x bc/8 - ab x bc/8)
Axyz = 3ab x bc/8
Axyz/Aabcd = 3/8
Times 8.... --> 3
Assuming
A
B
C
D
is a parallelogram, the value of
S
can be proven as follows.
Join
B
and
D
to form segment
B
D
which is parallel to
X
Y
. The triangles
Δ
X
Y
C
and
Δ
D
B
C
are therefore similar, and since the side lengths of
Δ
X
Y
C
are half those of
Δ
D
B
C
, its area must be
4
1
of
Δ
D
B
C
, or
8
1
of
A
B
C
D
.
Join A and C now to form segment A C . Since B Y is half the length of B C , the area of Δ A B Y is half that of Δ A B C , or 4 1 of A B C D . Similarly, the area of Δ A B X is 4 1 of A B C D . Therefore, the answer is
S = 1 − 4 1 − 4 1 − 8 1 = 8 3 8 S = 3
It's also easy if you assume S is a constant for all parallelograms; you can then just assume A B C D is a square of side length 2 , and find the area of Δ A X Y is 4 − 1 − 1 − 2 1 = 2 3 . Therefore S = 4 ( 2 3 ) = 8 3
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