A wall 24 m long, 0.4 m thick and 6 m high is constructed with the bricks each of dimensions 
If the mortar occupies 
of the volume of the wall, then find the number of bricks used in constructing the wall.
Volume of cuboid = lbh,
where, l = length, b = breadth and h = height
For wall,
Length, l = 24 m
Breadth, b = 0.4 m
Height, h = 6 cm
Volume of wall = 24(0.4)(6) = 57.6 m3
As 
of this volume is covered by mortar, therefore 
of this volume is covered by bricks
For one brick,
Length, l = 25 cm = 0.25 m
[As 1 m = 100 cm]
Breadth, b = 16 cm = 0.16 m
Height, h = 10 cm = 0.10 m
Volume of one brick = lbh = 0.25(0.16)(0.10) m3
Hence Total No of bricks used in constructing the wall is 12960.
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