Area and Perimeter: Squares, Rectangles, Triangles

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Questions and Answers

A rectangular garden has a length of 20 meters and a width of 15 meters. A square garden has sides of 18 meters. Which garden has a larger area and by how much?

  • The rectangular garden is larger by 6 square meters.
  • The rectangular garden is larger by 24 square meters.
  • The square garden is larger by 6 square meters. (correct)
  • The square garden is larger by 24 square meters.

A wire of length 60 cm is bent into a square. If the same wire is bent into a rectangle with a length of 18 cm, what is the breadth of the rectangle?

  • 3 cm
  • 7 cm
  • 15 cm
  • 12 cm (correct)

What is the area of a parallelogram with a base of 15 cm and a height that is a third of its base?

  • 5 cm²
  • 45 cm²
  • 75 cm² (correct)
  • 225 cm²

A circular disc has a radius of 14 cm. What is the circumference of the disc?

<p>88 cm (C)</p> Signup and view all the answers

If the area of a square is 64 cm², what is the length of its diagonal?

<p>8√2 cm (B)</p> Signup and view all the answers

A rectangular park is 40 m long and 30 m wide. A 2 m wide path is built inside the park along its border. Find the area of the path.

<p>264 m² (A)</p> Signup and view all the answers

The side of an equilateral triangle is 8 cm. What is its area?

<p>16√3 cm² (D)</p> Signup and view all the answers

A rectangle is divided into two equal triangles by drawing a diagonal. If the area of the rectangle is 72 cm², what is the area of each triangle?

<p>36 cm² (A)</p> Signup and view all the answers

If the circumference of a circle is equal to the perimeter of a square, both having a value of 88 cm, which one has a larger area?

<p>The circle has a larger area. (D)</p> Signup and view all the answers

A square of side 4 cm is cut out from each corner of a rectangular sheet of length 24 cm and breadth 18 cm. The sides are then folded to form a box. What is the area of the base of the box?

<p>400 cm² (D)</p> Signup and view all the answers

Flashcards

Area vs. Perimeter

The area of a closed figure is the part of the plane it occupies. Perimeter is the distance around it.

Area of a square

Side multiplied by itself (side * side).

Perimeter of a rectangle

2 * (length + breadth) is how much fencing you need.

Area of a rectangle

Length multiplied by breadth (length * breadth).

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Parallelogram Area

Area of Parallelogram is Base x Height

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Circle Circumference

Circumference is the distance around a circle.

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What is Pi?

The ratio of a circle's circumference to its diameter.

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Circumference formula

Circumference equals pi multiplied by the diameter (Ï€d) or 2Ï€r.

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Area of a circle

Area of a Circle is πr squared

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Area Unit Conversion

When converting a unit of area to a smaller unit, the number of units becomes greater.

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Study Notes

  • The area of a closed figure refers to the portion of a plane it occupies, while the perimeter is the distance surrounding the figure.
  • Area is measured in square meters.

Perimeter and Area of Squares and Rectangles

  • Perimeter of a square = 4 × side
  • Perimeter of a rectangle = 2 × (length + breadth)
  • Area of a square = side × side
  • Area of a rectangle = length × breadth

Example Problem: Wire Rebent from Square to Rectangle

  • A wire shaped as a square with a 12 cm side is rebent into a rectangle with a 16 cm length.
  • The breadth of the rectangle is 8 cm
  • The square encloses more area (144 cm²) than the rectangle (128 cm²), even with the same perimeter.

Triangles as Parts of Rectangles

  • A rectangle's area equals the sum of the areas of two triangles formed by its diagonal.
  • The two triangles formed by the diagonal have the same area.
  • Area of each triangle for a rectangle = 1/2 × length × breadth
  • Area of each triangle for a square = 1/4 × (side)²

Area of a Parallelogram

  • Any side can be the base.
  • Height (altitude) - the perpendicular distance from the base to the opposite vertex.
  • Area = Base × Height

Example: Parallelogram Area

  • A parallelogram with a side of 17 cm and corresponding height of 7 cm has an area of 119 cm².

Area of a Triangle

  • Area = 1/2 × Base × Height
  • Area of an equilateral triangle = (√3 / 4) × (side)²
  • Congruent triangles always have the same area
  • Triangles with the same area are not necessarily congruent.

Circumference of a Circle

  • It's the distance around the circular location.
  • The ratio of a circle's circumference to its diameter is constant, denoted as Ï€ (pi).
  • Circumference (C) = Ï€d, where d is the diameter.
  • Circumference (C) = Ï€ × 2r
  • Ï€ is approximately 22/7 or 3.14.

Area of Circle

  • Area = Ï€r²
  • r is the radius of the circle.

Conversion Of Units

  • Units of area can be converted similarly to units of length.
  • 1 cm² = 100 mm²
  • 1 m² = 10000 cm²
  • 1 hectare = 10000 m²
  • Converting to a smaller unit results in a greater number of units.
  • Converting to a larger unit results in a smaller number of units.

Example: Area of Path around a Rectangular Park

  • A rectangular park is 55 m long and 20 m wide.
  • A 3.5 m wide path surrounds the park.
  • The area of the path is 574 m².

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