Answer :
hello , perimeter means length of total boundary . therefore for any triangle u can add all the sides of triangle.
ex- in triangle ABC ,sides of triangle is given AB=2cm ,BC=3cm and CA=4cm
then, perimeter of triangle ABC =AB + BC + CA
= 2cm + 3 cm +4 cm
perimeter of triangle ABC = 9cm
perimeter is the sum of the boundaries.so for finding perimeter we will add all the sides the ans obtained will the perimeter