If the edge of a cube is increased by 2 cm, the volume will increase by 488 cm3. What then will be the length of each edge of the cube?

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RRB ALP Previous Paper 8 (Held On: 13 Aug 2018 Shift 3)
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  1. 8 cm
  2. 6 cm
  3. 9 cm
  4. 7 cm

Answer (Detailed Solution Below)

Option 1 : 8 cm
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Detailed Solution

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Let the length of the cube be x cm

⇒ The length after 2 cm increase = x + 2 m

⇒ Initial volume = x3

⇒ Volume after increasing side = (x + 2)3

⇒ (x + 2)3 – x3 = 488

⇒ x3 + 6x2 + 12x + 8 – x3 = 488

⇒ 6x2 + 12x – 480 = 0

⇒ x2 + 2x – 80 = 0

⇒ (x – 8) (x + 10) = 0

⇒ x = 8, -10

⇒ x = 8 cm
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