If a diagonal AC of a parallelogram ABCD is of length 6 cm and side AB is of length 4 cm, then the length of side BC will be
> 2 cm
We know that sum of any two sides of a triangle is greater than its third side.
In the parallelogram ABCD, consider the triangle ABC.
We have, AB + BC > AC
BC > 6 cm - 4 cm
BC > 2 cm