Question

Marry wants to decorate her christmas tree. She wants to place the tree on a wooden box covered with coloured papers with pictures of santa cluas. She must know the exact quantity if paper to buy for this purpose. If the box has length 80 cm , breadth 40cm and height 20cm respectively , then how many square sheets of paper of side 40 cm would she require ?

Answer 1

There a mistake in the answer
Sorry I am not able to delete or edit my pic

The total suface area should be double
(I only considered 3 rectangle in the answer but there are 6)
It should be 11200 cm^2

And then the no.of papers required = 11200/1600 = 7papers

Answer 2

Since Meri wants to paste the paper on the outer surface of the box the quantity of paper required would be equal to the surface area of the box which is of the shape of a cuboid the dimension of the box are :

Length is 80 cm

Breadth is 40 cm

Height is 20 cm

The surface area of the box

= 2(lb + bh + hl)

= 2[( 80 × 40 ) + ( 40 × 20 ) + ( 20 × 80)] cm²

= 2[ 3200 + 800 + 1600] cm²

= 2 × 5600 cm² = 11200 cm²

The area of each sheet of the paper = 40 × 40 cm²

= 1600 cm²

$Therefore, number of the sheets required = \frac{surface \: area \: of \: box}{area \: of \: one \: sheet \: of \: paper}$

$= \frac{11200}{1600} = 7$

So, She would require 7 Sheets.