Let the number of cubes that can be cut from bigger cube = n. Then,
n x Volume of smaller cube = Volume of bigger cube
Edge of smaller cube = 3 cm
Edge of bigger cube = 18 cm
n x (3)3 = (18)3
? n = (18 x 18 x 18) / (3 x 3 x 3)
? n = 6 x 6 x 6 = 216 cubes
External volume = 20 x 12 x 5 = 1200 cm3
Internal volume = (20 - 2) x (12 - 2) x (5 - 2)
= 18 x 10 x 3 = 540 cm3
? Volume of the metal = External volume - Internal volume
= 1200 - 540 = 660 cm3
Volume of rectangular box = 10 x 8 x 6 = 480 cm3
Volume of cubes = 6240 cm3
? Required boxes = Volume of cubes / Volume of rectangular box
= 6240/480 = 13
Hence, 13 boxes are needed.
Length of largest pencil that can be kept in a box
= Diagonal of box = ?l2 + b2 + h2
where, l = 8 cm, b = 6 cm , h = 2 cm
= ?64 + 36 + 4
= ?104 = 2?26
Volume (new cube) = (13 + 63 + 83 ) = 729 cm3
a3 = 729
? a = ? 729
? Surface area of the new cube = 6a2
= 6 x 92 = 486 sq cm
Surface area/2 = 486/2 = 243 sq cm
Volume = 1989
? lbh = 1989
? 17 x 13 x h = 1989
? h = 1989/(17 x 17) = 9 cm
Surface area of cube which can be painted = 6(Side)2 = 6(2)2 = 24 cm2
Now, surface area of cuboid which can be painted
= 2(lb + bh + lh)
= 2(2 + 6 + 3) = 22 cm
Total surface area of both cube and cuboid
= 22 + 24 = 46 cm2 < 54 cm2
Therefore, both cube and cuboid can be painted.
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
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
Capacity of tank = = 50000 L = 50 m3 [? 1L = 1/1000 m3 ]
? Breadth = 50/(2.5 x 10) = 2 m
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
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