Question

how many cubes of sides 3cm in the wooden block in shape of cuboid whose length, breadth, height is 21×9×8.how much wood is wasted?

Answer 1

56 is the answer just equate the volume of both that is lbh amd a³

Answer 2

Hi user 

Here's your answer 
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First let us write the formula of volume each solid.

Cube = a³ ( Here ' a '  is the side of the cube )

Cuboid = Length * Breadth * Height 

Given Dimensions:

Cube: a = 3 cm

Cuboid: Length = 21 cm

Breadth = 9 cm 

Height = 8 cm.

Let the number of cubes required to make that cuboid be " n "

So,

= n * Volume of cube = Volume of cuboid.

= n * ( 3 )³ = 21 * 9 * 8

= n * 27 = 21 * 72 

= n * 27 = 1512

=> n = 1512 / 27 = 56

Hence 56 cubes are required to make that wooden block. 

Since the number of cubes is perfectly required there is no wastage of wood.
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Hope my answer is correct 

Have a good day :-)