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Published byOliver York Modified over 8 years ago

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There are some patterns that occur when we multiply a number by a power of ten, such as 10, 100, 1000, 10,000, and so on.

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76.543 10 = 765.43 76.543 100 = 7654.3 76.543 100,000 = 7,654,300 Decimal point moved 1 place to the right. Decimal point moved 2 places to the right. Decimal point moved 5 places to the right. 2 zeros 5 zeros 1 zero The decimal point is moved the same number of places as there are zeros in the power of 10.

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Move the decimal point to the right the same number of places as there are zeros in the power of 10. Multiply: 3.4305 100 Since there are two zeros in 100, move the decimal place two places to the right. 3.4305 100 = 343.053.4305 = Multiplying Decimals by Powers of 10

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Do each multiplication problem mentally: 1 4162 100 2 0.031652 × 10,000 3 73.426 100,000

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There are patterns that occur when dividing by powers of 10, such as 10, 100, 1000, and so on. The decimal point moved 1 place to the left. 1 zero 3 zeros The decimal point moved 3 places to the left. The pattern suggests the following rule..4562 10 456.2 1000 04562,. 456.2 Dividing Decimals by Powers of 10

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Move the decimal point of the dividend to the left the same number of places as there are zeros in the power of 10. Dividing Decimals by Powers of 10 Notice that this is the same pattern as multiplying by powers of 10 such as 0.1, 0.01, or 0.001. Because dividing by a power of 10 such as 100 is the same as multiplying by its reciprocal, or 0.01. To divide by a number is the same as multiplying by its reciprocal.

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Do each division problem mentally: 4 4162 ÷ 100 5 73.416 ÷ 10,000 6 41.32 ÷ 1000

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Notice that the number of decimal places in a decimal number is the same as the number of zeros in the denominator of the equivalent fraction. We can use this fact to write decimals as fractions. 037 100. 2 decimal places 2 zeros 0029 29 1000. 3 decimal places 3 zeros

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One way to compare decimals is to compare their graphs on a number line. Recall that for any two numbers on a number line, the number to the left is smaller and the number to the right is larger. To compare 0.3 and 0.7 look at their graphs. 010.3 3 10 7 0.7 0.3

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Comparing decimals by comparing their graphs on a number line can be time consuming, so we compare the size of decimals by comparing digits in corresponding places.

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Compare digits in the same places from left to right. When two digits are not equal, the number with the larger digit is the larger decimal. If necessary, insert 0s after the last digit to the right of the decimal point to continue comparing. Compare hundredths place digits. 3 5 < 35.63835.657< 35.63835.657

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For any decimal, writing 0s after the last digit to the right of the decimal point does not change the value of the number. 8.5 = 8.50 = 8.500, and so on When a whole number is written as a decimal, the decimal point is placed to the right of the ones digit. 15 = 15.0 = 15.00, and so on 15 = 15.0 = 15.00, and so on Helpful Hint

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7 Graph these numbers on a number line: 0.453, 0.445, 0.423, 0.460 8 Order from least to greatest: 0.321, 0.0945, 0.095, 0.3199

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