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Q.

PQRS is a rectangle in which length is two times the breadth and L is the midpoint of side PQ. With P and Q as centre, draw two quadrants. Find the ratio of rectangle PQRS to the area of the shaded region.


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a

14:3

b

13:4

c

12:3

d

12:5 

answer is A.

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Detailed Solution

Let's draw a diagram.
The point is that the length of the rectangle is twice the width of the rectangle.
So let the width of the rectangle be x units.
Then the length of the rectangle will be equal to 2x units.
Let L be the midpoint on the side PQ and P and Q the midpoints of the quadrants and the bounded region SLR denote the shaded portion.
IMG_256Now, we know that area of rectangle is equal to l×b  ,where l denotes length of rectangle and b denotes breadth of rectangle.
For rectangle PQRS, we have breadth b = x and length l = 2x
So, area of rectangle PQRS = 2x×x  
Area of rectangle PQRS =  2 x 2  
Now, we know that, quadrant is one-fourth part of a circle.
So, if area of circle is equals to  π r 2  , where r is equals to radius of circle, then,
The area of ​​the quadrant of the circle will be equal to Question Image.
Now, since L is the midpoint of the length of PQ and PQ = 2x units, now this midpoint divides the line segments into two equal parts, so,
PL = LQ = x units.
So the radius of the quadrant centered at P and Q will be equal to x units.
So, area of quadrant with centre P = area of quadrant with centre Q = 1 4 π x 2  units.
The, area of both quadrants together will be equals to  1 4 π x 2 + 1 4 π x 2  
Or, area of both quadrants together = 1 2 π x 2  
So, Area of shaded part = 2 x 2 1 2 π x 2  
On simplification, we get
Area of shaded part = x 2 (4π) 2  units
So, the ratio of rectangle PQRS to the area of shaded region = 2 x 2 x 2 4π 2  
On simplification, we get
 Ratio =  2 (4π) 2  
 Ratio = 4 (4π)  
 Ratio = 4 4 22 7  
 Ratio = 4 2822 7  
 Ratio = 28 6  
 Ratio = 14 3  
Hence, the ratio of rectangle PQRS to the area of the shaded region is equal to 14 : 3.
 
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