Question

1.A cuboidal block of 36 cm * 32 cm * 0.25 m Is melted and recast into cubes of edge 4 cm.
a)How many such cubes can be made?
b)What is the cost of silver plating the surface of these cubes @ Rs.0.75 / i)m² ii)cm² ?

Answer 1

first, you should find the volume of the cuboidal box
i.e = (36 x 32 x 25)cm = 28800 cm cube
then, find the volume of a cube that  is to be made out of the box = (4 x 4 x 4)cm cube = 64 cm cube.
no. of cubes = 28800/64 = 450
total surface area of 1 cube = 6 x 4² = 96 cm square
total surface area of 450 cubes = 96x 450 = 43200 cm square
ii)cost of silver painting these cubes @ 0.75 per cm² = 43200 × 0.75 =  32400 
i) cost of silver painting these cubes @ 0.75 per m²  = 
area in m² = 43200/10000 = 4.32m²
cost = 0.75 × 4.32 = 3.24

Answer 2

length of box = 36 cm
breadth of box = 32 cm
height f box = 0.25m = 25 cm

A) vol of cuboidal box = ( 36 x 32 x 25 ) Cm³
vol. of cube = (4 x 4 x 4 ) cm³

no. of cubes that can be made = 36x32x25/4x4x4
                                             = 450 cubes
B) 
i>  T.S.A. of cube in cm of 1 cube=6( side ) ²
                                      = 6(4)²
                                     = 6 x 16
                                     = 96 cm²

  cost of painting for 1 cube= Rs (0.75 x 96)
                           = Rs 72

 cost for painting for 450 cubes = Rs (450 x 72 )
                                                 = Rs 32400

ii> side of cube in m = 0.04 m 

T.S.A. of cube in m  for 1 cube = 6 ( 0.04 )²
                               = 6 x 0.0016
                              = 0.0096 m²

cost of painting  for 1 cube = Rs ( 0.75 x 0.0096)
                       =  Rs 0.0072

cost of painting  for 450 cubes = Rs ( 450 x 0.0072 )
                                              =  Rs 3.24