Question

9. Find the perimeter of the following:
(a) An equilateral triangle whose side is 15 cm.
(b) An isosceles triangle whose equal sides are
10 cm each and unequal side is 15 cm.
(c) An scalene triangle having sides 14 cm,
12 cm and 10 cm.
(d) A square of side 105 m.
(e) A regular pentagon of side 100 m.
(f) A regular decagon of side 55 m.
(g) A regular hexagon of side 60 cm.​

Answer 1

${\underline{\textsf{\textbf{ \color{grey}{\qquad Given\:: \qquad} }}}}$

• An equilateral triangle whose side is 15 cm.
• An isosceles triangle whose equal sides are 10 cm each and unequal side is 15 cm.
• An scalene triangle having sides 14 cm, 12 cm and 10 cm.
• A square of side 105 m.
• A regular pentagon of side 100 m.
• A regular decagon of side 55 m.
• A regular hexagon of side 60 cm.

${\underline{\textsf{\textbf{ \color{grey}{\qquad To\:find\:: \qquad} }}}}$

• Perimeter of given figures.

${\underline{\textsf{\textbf{ \color{grey}{\qquad Solution\:: \qquad} }}}}$

(a) Perimeter of an equilateral triangle whose side is 15 cm :

➲ㅤㅤPerimeter = 3 × side

➲ㅤㅤPerimeter = 3 × 15

➲ㅤㅤPerimeter = 45 cm

(b) Perimeter of an isosceles triangle whose equal sides are 10 cm each and unequal side is 15 cm :

➡ㅤㅤPerimeter = Sum of all sides

➡ㅤㅤPerimeter = 10 + 10 + 15

➡ㅤㅤPerimeter = 35 cm

(c) Perimeter of a scalene triangle having sides 14 cm, 12 cm and 10 cm :

➠ㅤㅤPerimeter = Sum of all sides

➠ㅤㅤPerimeter = 14 + 12 + 10

➠ㅤㅤPerimeter = 36 cm

(d) Perimeter of a square of side 105 m :

➥ㅤㅤPerimeter = 4 × side

➥ㅤㅤPerimeter = 4 × 105

➥ㅤㅤPerimeter = 420 m

(e) Perimeter of a regular pentagon of side 100 m :

➢ㅤㅤPerimeter = 5 × side

➢ㅤㅤPerimeter = 5 × 100

➢ㅤㅤPerimeter = 500 m

(f) Perimeter of a regular decagon of side 55 m :

➵ㅤㅤPerimeter = 10 × side

➵ㅤㅤPerimeter = 10 × 55

➵ㅤㅤPerimeter = 550 m

(g) Perimeter of a regular hexagon of side 60 cm :

→ㅤㅤPerimeter = 6 × side

→ㅤㅤPerimeter = 6 × 60

→ㅤㅤPerimeter = 360 cm

$\qquad{\underline{\textsf{\textbf{ \color{grey}{\qquad Solution\:completed \qquad} }}}}$

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Answer 2

_________________________

$\: \:$

9. Find the perimeter of the following :

$\: \:$

a) An equilateral triangle whose side is 15 cm.

$\: \:$

$\qquad : \implies \sf{Perimeter = 3 \times sides}$

$\: \:$

$\quad \sf : \implies{Perimeter = 3 \times 15}$

$\: \:$

$\quad : \implies \sf{Perimeter = 45cm}$

$\: \:$

_________________________

$\: \:$

b) An isosceles triangle whose equal sides are 10 cm each and unequal side is 15 cm.

$\: \:$

$\quad \small : \implies \sf{Perimeter = sum \: of \: all \: sides}$

$\: \:$

$\quad : \small \implies \sf{Perimeter = 10 + 10 + 15}$

$\: \:$

$\quad : \implies \sf{Perimeter = 35cm}$

$\: \:$

________________________

$\: \:$

c) An scalene triangle having sides 14 cm, 12 cm, 10 cm.

$\: \:$

$\quad \small : \implies \sf{Perimeter = sum \: of \: all \: sides}$

$\: \:$

$\quad \small : \implies \sf{Perimeter = 14 + 12 + 10}$

$\: \:$

$\quad : \implies \sf{Perimeter = 36cm}$

$\: \:$

________________________

d) a square of side 105 m.

$\: \:$

$\quad : \implies \sf{Perimeter = 4 \times sides}$

$\: \:$

$\quad : \implies \sf{Perimeter = 4 \times105 }$

$\: \:$

$\quad : \implies \sf{Perimeter = 402cm}$

$\: \:$

_________________________

$\: \:$

e) A regular Pentagon of side 100 m.

$\: \:$

$\quad : \implies \sf{Perimeter = 5 \times sides}$

$\: \:$

$\quad : \implies \sf{Perimeter = 500cm}$

$\: \:$

_________________________

$\: \:$

f) A regular decagon of side 55 m.

$\: \:$

$\quad : \implies \sf{Perimeter = }10 \times sides$

$\: \:$

$\quad : \implies \sf{Perimeter = 550cm}$

$\: \:$

_________________________

$\: \:$

g) A regular hexagon of side 60 cm.

$\: \:$

$\quad : \implies \sf{Perimeter = 6 \times sides}$

$\: \:$

$\quad : \implies \sf{Perimeter = 6 \times 60}$

$\: \:$

$\quad : \implies \sf{Perimeter = 360cm}$

$\: \:$

________________________