Question

the internal length, breadth and height of a closed box are 1m,80 cm and 25 cm. respectively. if its sides are made up of 2.5cm thick wood.
find the space occupied by the box, tge volune of wood used to make the box.
find the weight of the box, if one cu.cm of wood weighs 10g

Answer 1

External edge lengths of the box:  
   100 + 2*2.5 = 105 cm ,  80+2*2.5 = 85 cm,    25+ 2*2.5 = 30cm

space occupied by the box = external volume of the box
  = 105 * 85 * 30 cm³
  = 267, 750 cm³ = 0.267750 m³

Internal volume (volume of empty space inside)
  = 100 cm * 80 * 25 cm = 200, 000cm³

Volume of the wood used =  267, 750 - 200, 000 = 67, 750 cm³

Weight of the box = volume * density
                             = 67, 750 cm³ * 10 gm/cm³ 
                              = 677, 750 gms = 677.750 kg