As shown above, six circles are inscribed in one rectangle. They all have equal radii, and the total area of the circles is 2 π Find the area of the rectangle.
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Let the radius of each circle be r ⟹ d i a m e t e r = 2 × r
Now, length of the rectangle is combination of diameters of 3 equal circles and breadth of the rectangle is the combination of diameters of 2 equal circles.
⟹ l = 3 × 2 r = 6 r
⟹ b = 2 × 2 r = 4 r
Now, area of 6 equal circles is 2 π .
6 × 2 π r 2 = 2 π
⟹ r 2 = 3 1
Now, area of the rectangle = l × b
⟹ 6 r × 4 r = 2 4 r 2 = 2 4 × 3 1 = 8
Therefore, area of the rectangle is 8 .
Let r be the radius of one of the gray circles.
Since the total area of all the circles combined is 2 π , that means 6 π r 2 = 2 π ⟹ r 2 = 3 1 ⟹ r = 3 1
Because the circles are inscribed in the rectangle, that means the dimensions of the rectangle are 6 r × 4 r :
3 6 × 3 4 = 3 2 4 = 8
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To begin solving this problem, notice that the length and height of the rectangle can be written in terms of the radius, r , of the circles as such:
L e n g t h = 6 r
H e i g h t = 4 r
Now to solve for the area of the rectangle, solving for the radius is prominent. As said in the given, the combined area of all the circles is 2 π . Using this information, we can solve for the area of one circle as such:
Let x = area of one circle.
∴ 6 x = 2 π ⇒ 3 x = π ⇒ x = 3 π
Now that we have solved for the area of one circle, we can solve for the radius by setting it equal to the formula for finding the area of a circle as such:
3 π = π r 2 ⇒ 3 1 = r 2 ⇒ r = 3 1
Now that we know the value of the radius, r , we can reliably solve for the area of the rectangle as such:
L e n g t h = 6 × 3 1 ⇒ L e n g t h = 3 6
H e i g h t = 4 × 3 1 ⇒ H e i g h t = 3 4
∴ Area of the Rectangle = 3 6 × 3 4 ⇒ 3 2 4 ⇒ 8