Final answer:
When performing the addition of 2.016 g and 15.99 g, the result should be rounded to the hundredths place, giving 18.01 g. For multiplication, like 0.6238 cm and 6.6 cm, round to the least number of significant figures, resulting in 4.1 cm².
Step-by-step explanation:
To perform a calculation with proper significant figures, we should follow the rule of precision based on the least precise number. For example, when adding 2.016 g (measured to the thousandths place) and 15.99 g (measured to the hundredths place), the sum is 18.006 g. However, since 15.99 g has the least number of decimal places, we must round the final answer to the same precision, which is the hundredths place. Therefore, the result is 18.01 g after rounding.
Another example is the multiplication of 0.6238 cm by 6.6 cm. The former has four significant figures, while the latter has two, so the answer must be limited to two significant figures as it is the lower precision. This means that the product 4.11708 cm² would be rounded to 4.1 cm².
In summary, always round your result to the least precise measurement to ensure your answer conforms with significant figure rules.