# (i)The cost of constucting a wall 8 m long , 4m high and 20 cm thick at rate of rs 25 per m^3 is (ii)A cube whose volume is 1/8 cubic cm is placed on top of a cube whose volume is 1 cm ^3.the 2 cubes are then placed on top of a 3rd cube whose vol is 8 cm^3.the height of stacked cubes is (iii)the number of cubes of side 3 cm that can be cut froma cuboid of dimensions 10 cm *9cm*6 cm is answer all

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by rajusetu
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2015-03-01T18:40:04+05:30

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1. given l=8m, h=4m and b=20/100 = 1/5m
then volume of wall = lbh
= 8×4×1/5
= 32/5
= 6.2m³
given per m³ = 25 rs
per 6.2m³ = 6.2×25
= 160 Rs
3. n×volume of cube= volume of cuboid
n×a³=lbh
n = 10×9×6/3³
= 10×9×6/27
= 20 cubes
2. we know that in cube all sides are equal .so the length of side is height
given for first cube volume = 1/8cm³
i.e., a³=1/8
a = 1/2cm
i.e., height of 1st cube is 1/2 cm
given for second cube volume a³=1
a = 1 (a is not -1 because heights are never calculate in negative)
so height of second cube is 1cm
then given volume of third cube is 8 cm³
a³=8
a= 2 cm
so height of third cube is 2cm
then the height of resulting staked cubes is sum of the hieghts of three cubes
= 1/2 + 1+2
= 1+2+4/2                (by taking lcm)
= 7/2
= 3.5 cms
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2015-03-01T21:01:53+05:30
1-   length of wall = 8 m
breadth of wall = 20cm = 0.2 m
height of wall = 4m

vol. of wall = lbh
=( 8 x 4 x 0.20 )m³
=6.4 m³
cost of building = Rs (6.4 x 25)
= Rs 160

2-   height of cube whose vol. is 1/8 cm³
side³ = 1/8
side = ∛1/8
side=1/2 = 0.5 cm

height of cube whose vol. is 1 cm³
side³ = 1
side = ∛1
side = 1 cm

height of cube whose vol. is 8 cm³
side³ = 8
side = ∛8
side = 2

total height = (0.5 +1+2) = 3.5cm

3-vol. of cuboid = (10 x 9 x 6 ) cm³ = 540cm³
vol of cube =(3)³ cm³

no of cubes that can be cut = 540/27
=20 cubes