The length of a rectangle is 5mm more than twice the width. if the area is 168 square mm, fine the dimensions of the rectangle.

Let the width be w and length be l and area be a.

l= 5 + 2w

now, area = length x breadth

=> a = l x b
=> 168 = (5+2w ) x w

=>168 = 5w + 2w^2

=>on factorising, w= 8 

hence dimensions : 21 x 8 mm