**Question:**

**The density of a material in SI unit is $128 \mathrm{~kg} \mathrm{~m}^{-3} .$ In certain units in which the unit of length is $25 \mathrm{~cm}$ and the unit of mass is $50 \mathrm{~g}$, the numerical value of density of the material is:**

40

16

640

410

Question of from chapter.

JEE Main Previous Year 2019

Correct Option: 1

**Solution:**

(a) Density of material in SI unit,

$=\frac{128 \mathrm{~kg}}{\mathrm{~m}^{3}}

Density of material in new system$

$=\frac{128(50 \mathrm{~g})(20)}{(25 \mathrm{~cm})^{3}(4)^{3}}=\frac{128}{64}(20)=40 \text { units }$

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