Two sides of a triangle are of length 3 cm and 8 cm. If the length of the third side is 'x' cm, then:

5 < x < 11

Two sides of the triangle are 3 cm and 8 cm respectively 

We know that,

Sum of length of two sides is greater than the third side in a triangle 

Let the third side be 'm' cm 

Now for 1st condition 

3 + m > 8 

= m > 5 

For condition 2nd 

3 + 8 > m 

= m < 11 

Values of 'm' concluded

= 5 < m < 11