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Measurements

• The perimeter of a closed figure is the distance covered along the boundary of the figure when we go around it once. Its units are cm, m etc.

Example: Let us find the perimeter of the following figure. Perimeter of ABCDEFGHIJA = AB + BC + CD + DE + EF + FG + GH + HI + IJ + JA

= (5 + 6 + 6 + 5 + 7 + 9 + 7 + 4 + 4 + 25) cm

= 78 cm

Perimeter of an equilateral triangle = 3 × length of a side
Perimeter of a square = 4 × length of a side
In general, perimeter of a regular closed polygon = Number of sides of the polygon × length of each side

Example:

If a farmer wants to fence a square field of length 50 m with 5 rounds of wire then what is the length of the wire required?

Solution:

Length of wire required = 5 × (perimeter of square field)

= 5 × (4 × side)

= 5 × [(4 × 50) m]

= 1000 m

• Perimeter of a rectangle = 2 (length + breadth)

Example:

What is the perimeter of a rectangular field whose length and breadth are 15 m and 8 m respectively?

Solution:

Perimeter of rectangular field = 2 (15 m + 8 m) =…

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