Question

Trailing zeros (those at the end) are significant only if the number contains a decimal point; otherwise, they are insignificant (they don't count). How many significant figures in 120000?

a) 2
b) 3
c) 4
d) 5

Answer 1

The number 120000 has two significant figures by default as the trailing zeros are presumed to be placekeepers without additional context or the use of scientific notation. The zeros would be significant if the number were presented with a decimal point or in scientific notation indicating precision.

Step-by-step explanation:

The number of significant figures in a given number depends on whether the zeros are serving as placekeepers or are part of a measured or exact quantity. When considering the number 120000, without further information or it being written in scientific notation, we cannot ascertain whether the trailing zeros are significant or not. Thus, the number could potentially have two, three, four, or five significant figures. However, because no decimal point is present, typically the zeros would be considered placekeepers, suggesting a default of two significant figures. To clarify the actual number of significant figures scientific notation should be used.

For instance, if 120000 is written as:

• 1.2 x 105 - it has two significant figures.
• 1.20 x 105 - it has three significant figures.
• 1.200 x 105 - it has four significant figures.
• 1.2000 x 105 - it has five significant figures.

Without this specificity, if no context is provided, the conservative approach is to assume there are two significant figures, which is answer (a).