Study MaterialsCBSE NotesPerimeter and Area Class 7 Notes Maths Chapter 11

Perimeter and Area Class 7 Notes Maths Chapter 11

The perimeter of a regular polygon = number of sides × length of one side

The perimeter of a square = 4 × side

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    Perimeter of rectangle = 2 × (l + b)
    (where l and b denote the length and breadth respectively of the rectangle)

    Area of a square = side × side

    Area of a rectangle = l × b

    Triangles as Parts of Rectangles
    The sum of the areas of the two triangles, into which a diagonal of a rectangle divides the rectangle, is the same as the area of the rectangle. Also, both the triangles are equal in area.
    Perimeter and Area Class 7 Notes Maths Chapter 11 1

    Generalising for Other Congruent Parts of Rectangles
    If we divide a rectangle into two congruent parts so that the area of one part is equal to the area of the other part, then
    area of each congruent part = \(\frac { 1 }{ 2 }\) (the area of the rectangle)

    Area of parallelogram = base × corresponding height (altitude)

    Conversion of Units
    1cm =10 mm
    1 cm2 = 100 mm2
    1 m2 = 100 × 100 = 10,000 cm2
    1 km2 = 1000 × 1000 = 1,000,000 m2
    1 hectare = 10,000 m2

    Perimeter of square = 4 × side
    Perimeter and Area Class 7 Notes Maths Chapter 11 2

    Perimeter of Rectangle = 2 × (length + breadth)
    Perimeter and Area Class 7 Notes Maths Chapter 11 3

    Perimeter of triangle = sum of all sides of triangle = a + b + c
    Perimeter and Area Class 7 Notes Maths Chapter 11 4

    Area of square = side × side = (side)2
    Perimeter and Area Class 7 Notes Maths Chapter 11 5

    Area of Rectangle = Length × Breadth = l × b
    Perimeter and Area Class 7 Notes Maths Chapter 11 6

    Area of Triangle = \(\frac { 1 }{ 2 }\) × Base × Height (Altitude)
    Perimeter and Area Class 7 Notes Maths Chapter 11 7

    Area of a parallelogram = Base × Height
    Perimeter and Area Class 7 Notes Maths Chapter 11 8

    The distance around a circular region is known as its circumference.

    Circumference of a circle = πd = π(2r) = 2πr. where d is diameter and r is the radius.
    Perimeter and Area Class 7 Notes Maths Chapter 11 9

    Area of a circle = πr2
    π = \(\frac { 22 }{ 7 }\) or 3.14 (approximately).

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