Dimensions of rectangular sheet are 45 cm and 24 cm.

Let  cm be the side of each of the four squares cut off from each corner.

Then dimensions of the open box formed by folding the flaps after cutting off squares are  and  cm.

Let  denotes the volume of the open box.

= 

   and 

Now  = 0

  or 

 is rejected because at  length =  which is impossible.

   is the turning point.

At ,   [Negative]

·  is minimum at  i.e., side of each square to be cut off from each corner for maximum volume is 5 cm.