Math Problem Statement

Here is a picture of two squares and a circle.

Use the picture to explain why the area of the circle is more than 2 square units but less than 4 square units.

Here is a picture of two squares and a circle. Use the picture to explain why the area of the circle is more than 2 square units but less than 4 square units.

Solution

To analyze the image and explain why the area of the circle lies between 2 square units and 4 square units, let us break it down:

  1. Structure of the diagram:

    • The outer square encloses the circle perfectly, meaning the circle is inscribed in the square. The diameter of the circle equals the side length of the outer square.
    • There is also an inner square formed by the diagonals of the circle and the outer square.
  2. Relationship between the outer square and the circle:

    • If the side length of the outer square is ss, then the diameter of the circle is also ss.
    • The area of the outer square is s2s^2.
    • Since the circle is inscribed, its radius is r=s2r = \frac{s}{2}, and its area is given by πr2=π(s2)2=πs24\pi r^2 = \pi \left(\frac{s}{2}\right)^2 = \frac{\pi s^2}{4}.
  3. Relationship between the inner square and the outer square:

    • The inner square is formed by joining the midpoints of the sides of the outer square. Its side length is the diagonal of the smaller squares within the outer square, calculated as s2\frac{s}{\sqrt{2}}.
    • Therefore, the area of the inner square is (s2)2=s22\left(\frac{s}{\sqrt{2}}\right)^2 = \frac{s^2}{2}.
  4. Bounding the area of the circle:

    • The area of the circle πs24\frac{\pi s^2}{4} is less than the area of the outer square s2s^2 and greater than the area of the inner square s22\frac{s^2}{2}.
    • For a square with s=2s = 2, the area of the outer square is 44 square units, and the area of the inner square is 22 square units.
    • Since π\pi is approximately 3.14, the area of the circle becomes π44=3.14\frac{\pi \cdot 4}{4} = 3.14 square units. This confirms it is greater than 2 square units (inner square) but less than 4 square units (outer square).

Conclusion:

The visual relationship between the outer square, the inner square, and the circle helps us see that the circle’s area lies strictly between 2 square units (inner square) and 4 square units (outer square).


Would you like further clarification or additional mathematical proofs?

Related Questions:

  1. How do we calculate the exact area of a circle given its radius?
  2. What is the relationship between the inner square and the circle's diameter?
  3. Can you explain why the circle is closer in size to the outer square than the inner square?
  4. How does the value of π\pi affect this calculation?
  5. Can this reasoning be applied to other shapes, like an equilateral triangle inscribed in a circle?

Tip:

Remember, the area of a circle is proportional to the square of its radius, making it a powerful geometric comparison tool!

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Math Problem Analysis

Mathematical Concepts

Geometry
Areas of Circles
Properties of Squares

Formulas

Area of a square = side^2
Area of a circle = πr^2
Relationship between inscribed and circumscribed figures

Theorems

Pythagorean theorem (to find relationships between inner square and outer square diagonals)
Properties of inscribed circles

Suitable Grade Level

Grades 6-8