Let the edge of a square be x. and sum of its edges = 12 x
Now, by condition, x3 = 12x
? x(x2 - 12) = 0
? Its total surface area = 6x2 = 6(12) = 72 sq units
Volume of the cuboid = 720 cm3
Height of the cuboid = Volume of the cuboid / Base area of the cuboid
= 720 / 72 = 10 cm [By Hit Trail]
Surface area of the cuboid = 2 (lb + bh + hl)
= 2(9 x 8 + 8 x 10 + 10 x 9 )
= 2 (72 + 80 + 90)
= 2 x 242
= 484 cm2
? It is obvious that length, breadth and height of the cuboid is 9 cm, 8 cm and 10 cm.
Surface area of 1 brick
= 2 (lb + bh + lh)
= 2(22.5 x 10 + 10 x 7.5 + 7.5 x 22.5)
= 2(225 + 75 + 168.75)
= 2 x 468.75 = 937.50 cm2
= 93750/(100 x 100) = 0.09375 sq m
? Number of bricks = Total area/Surface area of 1 brick
= 9.375 / 0.09375 = 100
Capacity of tank = = 50000 L = 50 m3 [? 1L = 1/1000 m3 ]
? Breadth = 50/(2.5 x 10) = 2 m
Given, lb = 120 sq cm., bh = 72 sq cm, lh = 60 sq cm.
? lb x bh x lh = 120 x 72 x 60
? (lbh)2 = 120 x 72 x 60
? lbh = ?120 x 72 x 60
= ?12 x 10 x 12 x 6 x 10 x 6
= 12 x 10 x 6 = 720 cm3
Let length, breadth and height be 4k, 3k and 2k, respectively.
Whole surface area = 2(lb + bh + lh)
? (lb + bh + lh) = 8788/2 = 4394
? (4 x 3 + 3 x 2 + 2 x 4 ) k2 = 4394
? 26k2 = 4394
? k2 = 169
? k = 13
? Length = 4k = 4 x 13 = 52 cm
Here, x = y = -19%
According to the formula,
Percentage decrease in surface area
= [x + y + xy/100]%
= [- 19 - 19 + (-19) x (-19) /100]%
=[-38 + 361/100]%
= [-38 + 3.61]% = -34.39 %
Here, k = 12%
According to the formula,
Percentage increase in volume = [(1 + k/100)3 - 1] x 100%
= [(1 + 12/100)3 - 1] x 100%
= [(1.12)3 - 1] x 100%
= 0.404928 x 100% = 40.4928%
Given, r = 7 cm, h = 80 cm
Volume = ?r2h = (22/7) x 7 x 7 x 80
= 12320 cm3
Total surface area of cylinder = 2?r(h + r)
Given that, r = 14/2 = 7 cm, h = 40 cm
? Required total surface area = 2 x (22/7) x 7 x (40 + 7)
= 44 x 47 = 2068 sq cm
Given, lateral surface area = 94.2 sq cm
? 2?rh = 94.2
? r = 94.2/(2?h) = 94.2/(2 x 3.14 x 5) = 3 cm
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