Question

Two sides of a triangle are $12$ cm and $18$ cm. The perimeter of triangle is $45$ cm. Find the length of third side?

Answer 1

Length of one side of triangle
= $12$ cm

Length of second side of triangle
= $18$ cm

Perimeter of triangle
= $45$ cm

Since, perimeter of triangle
= Sum of length of all the 3 Sides

So, $45$ cm =$12$ cm + $18$ cm + Length of Third Side

Therefore,
Length of Third Side
= $45$cm - $(12\text{cm}+18\text{cm})$
= $45$ cm - $30$ cm
= $15$ cm

Hence, (c) is correct.