In $∆ABC$, if $\angle A={35}^0$ and $\angle B={65}^0$, then the longest side of the triangle is ______

Concept: Using angle sum property of triangle

∠A+∠B+∠C = 180^o

35^o + 65^o + ∠C =180^o

∠C = 180^o - 100^o = 80^o

Side opposite to largest angle is the longest side of any triangle.

Here ∠C is the largest angle and side opposite to it is AB.

So AB is the longest side.