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

(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

Answer 2

Step-by-step explanation:

(a) The perimeter of triangle = Sum of all sides

= 3 + 4 + 5

= 12 cm

The perimeter of triangle is 12 cm.

(b) The perimeter of an equilateral triangle = Sum of all sides

= 9 + 9 + 9

= 27 cm

The perimeter of triangle is 27 cm.

(c) The perimeter if an isoceles triangle = Sum of all sides

= 8 + 6 + 8

= 22 cm

The perimeter of triangle is 22 cm.