What do you mean by significant figures?

A sample of drinking water was found to be severely contaminated with chloroform, ${\mathrm{CHCl}}_3$, supposed to be carcinogenic in nature. The level of contamination was $15 \mathrm{ppm}$ (by mass).

Express this in percent by mass.

A sample of drinking water was found to be severely contaminated with chloroform, ${\mathrm{CHCl}}_3$, supposed to be carcinogenic in nature. The level of contamination was $15 \mathrm{ppm}$ (by mass).

Determine the molality of chloroform in the water sample. [Given Mass percent is $1.5\times {10}^{-3}$]

Express the following in the scientific notation:

$234,000$

Express the following in the scientific notation:

$8008$

Express the following in the scientific notation:

$500.0$

Express the following in the scientific notation:

$6.0012$