Question

The percentage of gold present in 20 carat gold is:
A. $\text{ }100\text{ }$
B. $\text{ }73.86\text{ }$
C. $\text{ }50\text{ }$
D. $\text{ }83.33\text{ }$

Answer 1

Hint: Think about the unit with which the purity of gold is measured and recall the definition of the unit carats. Consider the purest form of gold before trying to formulate the answer to this question.

Complete Solution :
Before calculating the percentage of gold that is present in 20 carat gold, let us first understand what carat really means and the number of carats the purest form of gold is supposed to have.
- A carat of gold is defined as the $\text{ }{{\dfrac{1}{24}}^{th}}\text{ }$ part of a whole. So, an article of gold is said to be 16 carats if it contains 16 parts of gold and 8 parts of the alloying metal that is used for strengthening the gold. One carat of gold is equivalent to $\text{ }4.16667{\scriptstyle{}^{0}/{}_{0}}\text{ }$ of the whole. The purest form of gold will contain $\text{ }100{\scriptstyle{}^{0}/{}_{0}}\text{ }$ gold and no alloying metal and will hence be 24 carat gold.
- In this question, the percentage of gold contained in an article that has its measure of purity as 20 carats is asked. We will find the answer to this question by cross multiplication and letting $x$ be the percentage of gold in 20 carat gold. If 24 carat gold is equivalent to $\text{ }100{\scriptstyle{}^{0}/{}_{0}}\text{ }$ gold then how many percent is 20 carat gold equivalent to ,
$\begin{align}
 & \text{ }\dfrac{24}{100} = \dfrac{20}{x} \\
 & \Rightarrow x = 83.333{\scriptstyle{}^{0}/{}_{0}}\text{ } \\
\end{align}$
So, the correct answer is “Option D”.

Note: Since gold is an extremely soft and rare metal, it gets deformed very easily. It would be counterproductive if we used items made up of such materials in day-to-day life as ornamental articles. Hence, gold is usually mixed with stronger alloys of copper and zinc so that the shape of the articles once made will not be deformed.