Math Problem Statement

solve

The diagram shows four identical circles drawn inside a square. Each circle touches two other circles and two sides of the square. The region inside the square that is outside the circles, shown shaded in the diagram, has a total area of 40 cm². Work out the perimeter of the square. Give your answer correct to 3 significant figures.

Solution

To solve this problem, we need to find the perimeter of the square given that the shaded area (the area outside the circles but within the square) is 40cm240 \, \text{cm}^2.

Step-by-Step Solution

  1. Define Variables and Geometry:

    • Let ss be the side length of the square.
    • Let rr be the radius of each circle.
  2. Area of the Square:

    • The area of the square, AsquareA_{\text{square}}, is s2s^2.
  3. Area of the Circles:

    • Since there are four identical circles, the total area of all the circles is 4×πr2=4πr24 \times \pi r^2 = 4\pi r^2.
  4. Shaded Area:

    • According to the problem, the shaded area (area of the square minus the area covered by the circles) is 40cm240 \, \text{cm}^2.
    • So, we have: s24πr2=40s^2 - 4\pi r^2 = 40
  5. Relationship Between ss and rr:

    • Each circle touches two sides of the square, meaning the diameter of each circle is equal to half of the side length of the square.
    • Therefore, 2r=s22r = \frac{s}{2} or s=4rs = 4r.
  6. Substitute s=4rs = 4r into the Shaded Area Equation:

    • Replace ss in the equation: (4r)24πr2=40(4r)^2 - 4\pi r^2 = 40 16r24πr2=4016r^2 - 4\pi r^2 = 40
  7. Solve for rr:

    • Factor out r2r^2 from the equation: r2(164π)=40r^2(16 - 4\pi) = 40
    • Divide both sides by 164π16 - 4\pi: r2=40164πr^2 = \frac{40}{16 - 4\pi}
    • Calculate r2r^2 and then rr using the approximation π3.14159\pi \approx 3.14159.
  8. Calculate the Side Length ss:

    • Substitute rr back to find s=4rs = 4r.
  9. Calculate the Perimeter of the Square:

    • The perimeter PP of the square is 4×s4 \times s.

Would

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Geometry
Area and Perimeter Calculation
Algebraic Manipulation

Formulas

Area of square: s^2
Area of a circle: πr^2
Shaded area equation: s^2 - 4πr^2 = 40
Relationship between square side length and circle radius: s = 4r

Theorems

Basic properties of circles and squares
Algebraic manipulation

Suitable Grade Level

Grades 10-12