Question

a chemist needs to know the mass of a sample of ( \text{na}_2\text{so}_4 ) to 3 significant digits. he puts the sample on a digital scale. this is what the scale shows:

if this measurement is precise enough for the chemist, round it to 3 significant digits.
otherwise, press the
o solution\ button.

Explanation:

Step1: Identify significant digits

Non - zero digits are significant. In the number \(47.22\), the digits \(4\), \(7\), \(2\), \(2\) are considered. Leading zeros (the two \(0\)s before \(4\)) are not significant.

Step2: Round to 3 significant digits

The first three significant digits are \(4\), \(7\), \(2\). The fourth digit is \(2\) (since \(47.22\)). According to the rounding rule (if the digit to be removed is less than \(5\), we leave the last digit of the rounded number as it is). So we keep the third digit (\(2\)) as it is.

Answer:

\(47.2\) g