SSC CGL 3 Sep 2016 Paper

The sum of two sides of a triangle is greater than the third side.
∴ AB + BC > AC
BC + CD > BD
CD + AD > AC
DA + AB > BD
On adding,
2 (AB + BC + CD + DA) > 2 (AC + BD)
⇒ AB + BC + CD + DA > (AC + BD)