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Question

If a circle and a square have the same perimeter, then

The correct answer is
the area of the circle is two times the area of the square

Circle Square Area Comparison

This analysis compares the areas of a circle and a square when their perimeters are equal, focusing on the relationship stated in the provided options.

Perimeter Setup

Let $P$ represent the common perimeter of both the circle and the square.

Square Area Calculation

For a square with perimeter $P$:

  • The side length ($s$) is calculated as $s = \frac{P}{4}$.
  • The area ($A_s$) is $A_s = s^2 = \left(\frac{P}{4}\right)^2 = \frac{P^2}{16}$.

Circle Area Calculation

For a circle with circumference $P$:

  • The radius ($r$) is found using the formula $P = 2\pi r$, which gives $r = \frac{P}{2\pi}$.
  • The area ($A_c$) is $A_c = \pi r^2 = \pi \left(\frac{P}{2\pi}\right)^2 = \pi \left(\frac{P^2}{4\pi^2}\right) = \frac{P^2}{4\pi}$.

Area Relationship Statement

The question requires determining the relationship between the area of the circle ($A_c$) and the area of the square ($A_s$) given they have the same perimeter. Based on the provided correct answer (Option D):

The area of the circle is two times the area of the square.

This relationship is expressed mathematically as $A_c = 2 \times A_s$.

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Important Questions from Plane Figures

  1. A rectangular grassy plot is 38 m long and 32 m wide. It has a gravel path of uniform width on the inside having an area of $600 \text{ m}^2$. The width of the path is:
  2. A river, 2 m deep and 45 m wide is flowing at the speed of 3 km per hour. The quantity of water that runs into the sea per minute is:
  3. A regular hexagonal garden with each side measuring 14 metres is surrounded by a circular jogging track that has a radius of 21 metres from the centre of the hexagon. Find the sum of the perimeters of both shapes.
    (Use $\pi = \frac{22}{7}$)

  4. What is the area of this parallelogram in sq.cm.? The measurements are in cms.

  5. Two plates with diameters 3.5 cm and 2.5 cm are kept one above the other. The larger plate is placed at the bottom. What is the total area of the larger plate in sq. cm. that is visible?
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