question_answer 6)

Page No. 213 Find the perimeter of each of the following shapes. (a) A triangle of sides 3 cm, 4 cm and 5 cm. (b) An equilateral triangle of side 9 cm. (c) An isosceles triangle with equal sides 8 cm each and third side 6 cm.

Answer:

(a) Let the given triangle be ABC. Here, AB = 3 cm, BC = 4 cm and CA = 5 cm. \[\therefore \] Perimeter of a triangle = Sum of lengths of all side \[=AB+BC+CA\] \[=(3cm+4cm+5cm)\] \[=(3+4+4)\,cm\,=12\,cm\] Hence, the perimeter of a triangle is 12 cm. (b) Let the given triangle be ABC. Here, \[AB=9cm,BC=9cm\] and \[CA=9cm\] \[\therefore \] Perimeter of an equilateral triangle = Sum of lengths of all sides \[=AB+-BC+CA\] \[=(9cm+9cm+9cm)=(9+9+9)cm=27cm\] Hence, the perimeter of a triangle is 27 cm. (c) Let the given isosceles triangle is ABC. \[\therefore \] Here, \[AB=8cm,BC=6cm\] and \[CA=8cm\] Perimeter of an isosceles triangle = Sum of lengths of triangle \[=AB+BC+CA=(8cm+6cm+8cm)\] \[=(8+6+8)cm=22cm\] Hence, the perimeter of an isosceles triangle is 22 cm.