Question

what will happen to the area of a rectangular if its length is doubled and breadth is tripled

Answer 1

Area of a rectangle is length * breadth 
if its length is doubled and breadth is tripled are will become six times it's initial area

Answer 2

Doubling the length quadruples the area. If side length=a, increasing the length by b means that the area is (ba)^3=(b^3)(a^3). The volume or equivalent in n dimensions is (ba)^n=(b^n)(c^n).