What will be the perimeter of a triangle of sides 3 cm, 4 cm and 5 cm?

The perimeter corresponds to the distance that is covered by a closed figure's boundary.

As we know the perimeter of triangle = Sum of lengths of all sides 

Given, the sides of the triangle are 3 cm, 4 cm, 5 cm.

So the perimeter,

= 3 cm + 4 cm + 5 cm 

= 12 cm

Therefore, the perimeter of given triangle is 12 cm.