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JEE Main201910 Jan 2019Morning ShiftPhysicsUnits and DimensionsActual

The density of a material in S I units is 128 k g m - 3 . In certain units in which the unit of length is 25 c m and the unit of mass is 50 g , the numerical value of density of the material is:

Options

  1. A410
  2. B16
  3. C40
  4. D640

Correct answer

C. 40

Step-by-step solution

ρ = M L 3 n 1 u 1 = n 2 u 2 ∴ 128 M 1 L 1 - 3 = n 2 M 2 L 2 - 3 ∴ n 2 = 128 × M 1 M 2 L 2 L 1 3 = 128 × 1000 50 × 25 100 3 = 128 × 20 × 1 64 = 40

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