Simplify

sqrt(5) * sqrt(3) is the same thing as sqrt(5*3). There is a property of square roots that $${\sqrt{{\mathtt{x}}}}{\mathtt{\,\times\,}}{\sqrt{{\mathtt{y}}}} = {\sqrt{{\mathtt{x}}{\mathtt{\,\times\,}}{\mathtt{y}}}}$$  

So simplified, the answer would be   $${\sqrt{{\mathtt{15}}}}$$