When making observations using two different instruments, it is important to keep in mind which tool will allow you to be the most accurate. The value with more significant digits othen gives a more accurate reading. The following activity allows you to find the diameter of a circle using two rulers with different markings.
Click on the image to explore this activity depicting the level of precision available for measurements taken using different scales.
Click "Start"and measure the diameter of the blue circle by dragging it to one of the
rulers. Enter the diameter using an appropriate number of significant figures and click
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Ruler A
Click to launch activity
Ruler B
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After opening the activity, click the Start button, and then drag the circle over one of the rulers to find its diameter
To count the number of significant figures in a value, use the following rules:
1. Nonzero integers are always significant.
2. Zeros between nonzero integers are always significant
3. Zeros that precede a decimal point are not significant
4. Zeros that follow a decimal point are not significant it and only if the number before the decimal point is zero. For example, in the number 0.01, neither zero is significant
5. Zeros after a nonzero digit are known to be significant it and only if the number contains a decimal point. If the number does not contain a decimal point, the zeros are either not significant or are ambiguous. For
example, the number 500. has three significant figures