A cube whose edge is 20 cm long has circleon each of its face painted black. what is the total area of unpainted surface of the cube if the cicles are of largest possible area ?
(a) 85.71 cm2 (b) 257.14 cm2
(c) 514.28 cm2 (d) 331.33 cm2

• total area of one side of cube = 20*20 = 400 cm2
  circle area = 3.14 * 10 * 10 = 314 cm2 (Since the circle is largest as possible. Therefore, diameter= 20 and radius = 10)
  unpainted area of one side of cube = 400-314 = 86cm2
  since cube has 6 faces. Therefore, the total area of unpainted region = 6*86 = 516 cm2
• 8 years agoHelpfull: Yes(8) No(0)
• Option C)
  The radius of the largest possible circle on the face of a cube will be 10 cm.
  Area of the circle = 22/7*10*10 = 314.2857 sq.cm.
  Total area of a face = 20*20= 400 sq.cm.
  Now the unpainted area on a face = 400 -314.2857=85.7143 sq.cm.
  Total unpainted area on 6 faces = 6*85.7143 = 514.28 sq.cm.
• 8 years agoHelpfull: Yes(5) No(0)
• 6*a^2 - 6*((a/2)^2)*(22/7) = surface area unpainted
  6*400 - 6*100*3.14
  2400 - 1884 = 516cm2
• 8 years agoHelpfull: Yes(1) No(0)
• Circle occupying maximum area inside a square is by having it's radius equal to half the length of side of the square. So here the radius of the circle will be 10cm. Area of square of length 20cm is 400cm. A cube of 20cm length will have 6 square faces of length 20cm. Area of circle of 10cm is 3.1416*10*10 = 314.16. The unoccupied on a square face area will be 400 - 314.16 = 85.84. Since there are 6 such faces, there will be six leftover spaces. Total leftover space is 6*85.84 = 515.04 which is nearer to 514.28(resulted due to precision).
• 6 years agoHelpfull: Yes(1) No(0)
• C) 514.28cm2
• 8 years agoHelpfull: Yes(0) No(0)
• c : 514.28
• 8 years agoHelpfull: Yes(0) No(0)
• c)514.28 cm2
  explanation:-6*(20*20-3.14*10*10)
• 8 years agoHelpfull: Yes(0) No(0)
• radius of circle =10cm.
  area = 3.1417*10*10=314.17
  20*2-314.17=85.83
  85.83*6=514.98
• 6 years agoHelpfull: Yes(0) No(0)
• Let's consider 1 side of a cube. Area of 1 side= 400cm^2
  Maximum area of Circle in 1 side=3.14*10*10=314cm^2
  So, Area left uncovered= 400-314=86cm^2
  Hence, total area of 6 faces= 86*6=516cm^2
• 6 years agoHelpfull: Yes(0) No(0)
• 6*20*20-6*20*20/4*3.13
• 5 years agoHelpfull: Yes(0) No(0)
• Total Surface area of cube = 6 X 20 X 20 = 2400 Sqcm
  Diameter of largest possible circle = Edge of cube i.e. 20 cm
  Area of all circles = 6 X 3.14 X 10 X 10 = 1884 Sqcm
  Area of unpainted surface = 2400 - 1884 = 516 Sqcm
  The nearest value to 516 is 514.28.
• 4 years agoHelpfull: Yes(0) No(0)