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Significant Figures Physical Science

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What is a significant figure? There are 2 kinds of numbers: –Exact: the amount of money in your account. Known with certainty.

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What is a significant figure? –Approximate: weight, heightanything MEASURED. No measurement is perfect.

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When to use Significant figures When a measurement is recorded only those digits that are dependable are written down.

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When to use Significant figures –If you measured the width of a paper with your ruler you might record 21.7cm. To a mathematician 21.70, or is the same.

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But, to a scientist 21.7cm and 21.70cm is NOT the same cm to a scientist means the measurement is accurate to within one thousandth of a cm.

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But, to a scientist 21.7cm and 21.70cm is NOT the same If you used an ordinary ruler, the smallest marking is the mm, so your measurement has to be recorded as 21.7cm.

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How do I know how many Sig Figs? Rule: All digits are significant starting with the first non-zero digit on the left.

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How do I know how many Sig Figs? Exception to rule: In whole numbers that end in zero, the zeros at the end are not significant.

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How many sig figs? x ,000,

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How do I know how many Sig Figs? 2 nd Exception to rule: If zeros are sandwiched between non-zero digits, the zeros become significant.

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How do I know how many Sig Figs? 3rd Exception to rule: If zeros are at the end of a number that has a decimal, the zeros are significant.

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How do I know how many Sig Figs? 3rd Exception to rule: These zeros are showing how accurate the measurement or calculation are.

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How many sig figs here? ,083,000,

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How many sig figs here? ,000,050,

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What about calculations with sig figs? Rule: When adding or subtracting measured numbers, the answer can have no more places after the decimal than the LEAST of the measured numbers.

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Add/Subtract examples 2.45cm + 1.2cm = 3.65cm, Round off to = 3.7cm 7.432cm + 2cm = round to 9cm

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Multiplication and Division Rule: When multiplying or dividing, the result can have no more significant figures than the least reliable measurement.

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A couple of examples cm x 2.45cm = cm 2 Round to 139cm cm x 9.6cm = ?

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The End Have Fun Measuring and Happy Calculating!

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