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Question

Four circles of equal radius are drawn with centers, A, B, C and D such that ABCD is a square of side 14 cm and the circles touch externally as in the figure. The area of the shaded region bounded by the 4 circles is: (Take $\pi = \frac{22}{7}$)

The correct answer is
24 cm²

To find the area of the shaded region, we first need to understand the arrangement of the circles and the square. The circles are arranged so that they touch each other externally, and their centers are at the vertices of the square ABCD. Given:

  • Side of the square, \(s = 14 \, \text{cm}\)

The radius of each circle is half of the side of the square because the centers of two touching circles (such as A and B) are 14 cm apart, which is equal to one side of the square ABCD. Therefore:

  • Radius of each circle, \(r = \frac{14}{2} = 7 \, \text{cm}\)

Next, we calculate the area of the shaded region formed by the intersection of the four circles. The shaded area is the area of the square minus the sum of the areas of the four quarter circles in each corner of the square.

Step 1: Calculate the area of the square:

  • \(\text{Area of the square} = s^2 = 14^2 = 196 \, \text{cm}^2\)

Step 2: Calculate the area of one circle:

  • \(\text{Area of one circle} = \pi r^2 = \frac{22}{7} \times 7^2 = 154 \, \text{cm}^2\)

Step 3: Calculate the area of the four quarter circles inside the square:

  • \(\text{Area of four quarter circles} = 4 \times \frac{1}{4} \times \text{Area of one circle} = \text{Area of one circle} = 154 \, \text{cm}^2\)

Step 4: Calculate the shaded area:

  • \(\text{Shaded area} = \text{Area of the square} - \text{Area of four quarter circles} = 196 - 154 = 42 \, \text{cm}^2\)

On reviewing, we notice a mistake in the available answer choices. The correct calculation suggests that the shaded area should be 42 cm² rather than the provided solution of 24 cm².

Therefore, the correct answer should be 42 cm².

Diagram of four touching circles with a shaded region in the center.
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Important Questions from Circles

  1. The sum of the radius and diameter of a circle is 84 cm. What is the circumference of this circle?

  2. The maximum area of a right-angled triangle inscribed in a circle of radius r is

  3. The tangent at a point C of a circle and diameter AB when extended intersect at D, if ∠DCA = 110°, then ∠CBA is equal to

  4. The equation of a circle with diameters are 2x - 3y + 12 = 0 and x + 4y - 5 = 0 and area of 154 sq. units is

  5. The internal center of similitude of two circles $ (x - 1)^2 + (y - 3)^2 = 4 $ and $ (x + 5)^2 + (y - 9)^2 = 16 $ is

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