Previous Year Question
What is the percentage of pure gold in 18-carat gold?
A.
80%
B.
60%
C.
100%
D.
75%
Correct Answer: D
Detailed Solution
The purity of gold is expressed in karats, with 24-karat gold representing the standard for pure gold.
Therefore, the proportion of pure gold in 18-karat gold is:
18/24 × 100 = 75%
Thus, 18-karat gold contains 75% pure gold and approximately 25% other metals.
The Bureau of Indian Standards (BIS) also uses the marking 18K750. A fineness of 750 means 750 parts of pure gold per 1000 parts, i.e. 75% purity.
Remember:
24K ≈ Pure gold
22K916 = 91.6%
18K750 = 75.0%
14K585 = 58.5%