Question

Lactometer is a form of hydrometer used to measure the purity of milk. If in milk, the lactometer sinks up to the mark of 1, which one of the following conclusions can be drawn?

• A. The milk in the liquid is only 50% pure
• B. The milk in the liquid is only $\left(\frac{3}{4}\right)$th of it
• C. The milk in the liquid is only $\left(\frac{1}{4}\right)$th of it (25% pure)
• D. The milk is 100% pure

Answer 1

The correct option is C The milk in the liquid is only $\left(\frac{1}{4}\right)$th of it (25% pure)

Lactometer works on buoyancy force by cream-content in the milk.

More the cream, more would be the buoyancy force and less would the Lactometer sink in the milk.

If it sinks up to the mark of 1, it implies the pure milk content is 25% of the total volume of liquid, in which the Lactometer was placed.