Question

the length of the two sides of a triangle is 4cm and 5cm and the perimeter is 15 cm. what is the length of third side of the triangle​

Answer 1

⇒  The sum of the lengths of any two sides in a triangle is always greater than the length of the third side in the triangle.

⇒  The differnce of the lengths of any two sides in a triangle is always lesser than the length of the third side in the triangle.

⇒  The difference between 4cm and 7cm is  

3cm and their sum is 11cm.

⇒  To ensure that the above mentioned rule is not violated, the possible length of the third side has got to be greater than 3cm and lesser than 11cm.

⇒  So from the given options 6cm is less than  

11cm and greater than 3cm

∴  The length of the third side of triangle is 6cm