OA coming after a few people try answer..
In the square below, 12w = 3x = 4y. What fractional part of the square is shaded?
A) 2/3
B) 14/25
C) 5/9
D) 11/25
E) 3/7
Difficult Math Question #11
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Soln:
Assume - 12w = 3x = 4y = 12
=> w = 1; x = 4; y = 3
Side of square = w+x = 5 = 2w + y
there are four triangles:
Area T1 = 1/2*w*x = 1/2*1*4 = 2
Area T2 = 1/2*w*x = 1/2*1*4 = 2
Area T3 = 1/2*x*y = 1/2*4*3 = 6
Area T4 = 1/2*w*2w = 1/2*1*2*1 = 1
Total area of triangles = AT1 + AT2 + AT3 + AT4 = 11
thus area of shaded region = Area of square - total area of triangles = 5^2 - 11 = 14
thus fractional part of square that is shaded = area of shaded region/area of square = 14/25
Ans: (B)
Assume - 12w = 3x = 4y = 12
=> w = 1; x = 4; y = 3
Side of square = w+x = 5 = 2w + y
there are four triangles:
Area T1 = 1/2*w*x = 1/2*1*4 = 2
Area T2 = 1/2*w*x = 1/2*1*4 = 2
Area T3 = 1/2*x*y = 1/2*4*3 = 6
Area T4 = 1/2*w*2w = 1/2*1*2*1 = 1
Total area of triangles = AT1 + AT2 + AT3 + AT4 = 11
thus area of shaded region = Area of square - total area of triangles = 5^2 - 11 = 14
thus fractional part of square that is shaded = area of shaded region/area of square = 14/25
Ans: (B)
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OA:
Since 12w=3x=4y,
w:x=3:12=1:4 and x:y=4:3
so, w = 1
x = 4
y = 3
the fractional part of the square is shaded:
{(w+x)^2 - [(1/2)wx + (1/2)wx +(1/2)xy + (1/2)w(2w)]}/(w+x)^2
= {(w+x)^2 - [wx + (1/2)xy + w^2)]}/[(w+x)^2]
=[(5^2) -(4+6+1)]/(5^2)
= (25 - 11)/25
= 14/25
Since 12w=3x=4y,
w:x=3:12=1:4 and x:y=4:3
so, w = 1
x = 4
y = 3
the fractional part of the square is shaded:
{(w+x)^2 - [(1/2)wx + (1/2)wx +(1/2)xy + (1/2)w(2w)]}/(w+x)^2
= {(w+x)^2 - [wx + (1/2)xy + w^2)]}/[(w+x)^2]
=[(5^2) -(4+6+1)]/(5^2)
= (25 - 11)/25
= 14/25
replace x by 4w and y by 3w800guy wrote:OA coming after a few people try answer..
In the square below, 12w = 3x = 4y. What fractional part of the square is shaded?
A) 2/3
B) 14/25
C) 5/9
D) 11/25
E) 3/7
now each side is equl to 5w
area of square = 25w^2
now find out area of 4 triangles on corner
w*x/2 + w*x/2 + w*2w/2 + x*y/2
=> w*4w/2 + w*4w/2 + w*2w/2 + 3w*4w/2 = 11w^2
area of gray part = 25w^2 - 11w^2 = 14w^2
ratio = 14/25
(0) Fraction = Shaded Area / Square Area
(1) Square Area: The area of a square is the product of it's sides, thus: Square Area
= (x+w)²
(2) Shaded Area
= Square Area - White Parts
(2a) White Parts
= Sum of the 4 Triangle Areas
= 0.5xw + 0.5xw + 0.5w2w + 0.5xy
= xw + w² + 0.5xy
(2b) Shaded Area
= Square Area - White Parts
= (x+w)² - xw - w² - 0.5xy
= (x²+2xw+w²) - xw - w² - 0.5xy
= x² + xw - 0.5xy
(3) Fraction
= Shaded Area / Square Area
= (x² + xw - 0.5xy) / (x+w)²
(4) 12w = 3x = 4y
==> x = 4w, y = 3w
(5) Fraction
= (x² + xw - 0.5xy) / (x+w)²
= ((4w)² + 4ww - 2w3w) / (4w+w)²
= (16w² + 4w² - 6w²) / (5w)²
= (14w²) / (5w)²
= 14w² / 25w²
= 14/25
(1) Square Area: The area of a square is the product of it's sides, thus: Square Area
= (x+w)²
(2) Shaded Area
= Square Area - White Parts
(2a) White Parts
= Sum of the 4 Triangle Areas
= 0.5xw + 0.5xw + 0.5w2w + 0.5xy
= xw + w² + 0.5xy
(2b) Shaded Area
= Square Area - White Parts
= (x+w)² - xw - w² - 0.5xy
= (x²+2xw+w²) - xw - w² - 0.5xy
= x² + xw - 0.5xy
(3) Fraction
= Shaded Area / Square Area
= (x² + xw - 0.5xy) / (x+w)²
(4) 12w = 3x = 4y
==> x = 4w, y = 3w
(5) Fraction
= (x² + xw - 0.5xy) / (x+w)²
= ((4w)² + 4ww - 2w3w) / (4w+w)²
= (16w² + 4w² - 6w²) / (5w)²
= (14w²) / (5w)²
= 14w² / 25w²
= 14/25