Question

to construct a wall 24m long,0.4m thick and 6m high,bricks of dimensions 25cm*16cm*10cm each are used.if the mortar occupies 1/10th of the volume of the wall,find the number of bricks used.

Answer 1

dimension of wall = 24m × 0.4m × 6m
volume of wall = 24×0.4×6 = 57.6 m³

dimension of brick = 25cm × 16cm × 10m
volume of one brick = 25×16×10 = 4000cm³
1m³ = 100cm×100cm×100cm = 1000000cm³
1 cm³ = 1/1000000 m³
4000 cm³ = 4000/1000000 m³ = 0.004 m³

volume of mortar = (1/10) of volume of wall
                          =(1/10)×57.6 = 5.76 m³ 
volume of all bricks = 57.6 - 5.76 = 51.84 m³
no. of bricks = (volume of all bricks/volume of one brick)
                   = 51.84/0.004 = 51.84×1000/4
                   = 12960

Answer 2

Volume of wall=l*b*h=(2400*40*600)cm³
Volume of bricks=l*b*h=(25*16*10)cm³
1/10 of the wall consists of mortar
Therefore, 1-1/10=9/10 of the wall consists of mortar
no.of bricks=9/10*volume of wall/volume of bricks
(9/10*2400*40*600)/25*16*10=129600
Therefore,129600 bricks will be used.