Question

A person is considered to be suffering from lead poisoning if its concentration in him is more than 10 micrograms of lead per decilitre of blood. This concentration in parts per billion is:

• A. 1
• B. 10
• C. 100
• D. 1000

Answer 1

The correct option is C 100

$10\mu g=10\times {10}^{-6}\text{g}={10}^{-5}\text{g}$
$1\text{decilitre}=0.1\text{L}=100\text{ml}$
Thus, $100\text{ml}$ of blood contain lead = ${10}^{-5}\text{g}$
$\therefore 1\text{billion}\left({10}^9\right)$ parts will contain:
$=\frac{{10}^{-5}}{100}\times {10}^9={10}^2=100$ parts