Presentation on theme: "L E S S O N 13.5 Multiplying Decimals 0.7"— Presentation transcript:
1 L E S S O N13.5Multiplying Decimals0.7You can use graph paper to model decimal multiplication. Here is a model of the product of 0.7 and 0.3.0.31Because 21 of the 100 squares are shaded, 0.7 0.3= 0.21.1
2 L E S S O NMultiplying Decimals13.50.7You can use graph paper to model decimal multiplication. Here is a model of the product of 0.7 and 0.3.0.31Because 21 of the 100 squares are shaded, 0.7 0.3= 0.21.1NOTEBOOKMultiplying DecimalsWordsMultiply decimals as you would whole numbers. Then place the decimal point in the product. The number of decimal places in the product is equal to the sum of the number of decimal places in the factors.Numbers0.7 0.3 = 0.21
3 1 Multiplying Decimals 13.5 Multiplying Decimals 5.82 0.41 –––––– L E S S O N13.5EXAMPLE1Multiplying Decimals5.822 decimal places0.41–––––––––+2 decimal places5 8 2–––––––4 decimal places4213
4 Multiplying DecimalsL E S S O N13.5Checking Reasonableness To check that the product in Example 1 is reasonable, round each factor to the place value of the leading digit, then multiply. The leading digit of a number is the first nonzero digit.5.826Round to the nearest whole number.0.410.4Round to the nearest tenth.Because 6 0.4 = 2.4, the product of the previous example is reasonable.
5 2 Multiplying Decimals 13.5 Multiplying Decimals 6.45 18 –––––– ––– L E S S O N13.5EXAMPLE2Multiplying Decimals6.452 decimal places18––––––0 decimal places–––+5160645––––––116.102 decimal placesAfter you place the decimal point, you can drop any zeros at the end of an answer.ANSWER6.45 18 = 116.1CHECKBecause 6 20 = 120, the product is reasonable.
6 2 Multiplying Decimals 13.5 Multiplying Decimals 6.45 1.273 –––––– L E S S O N13.5EXAMPLE2Multiplying Decimals6.452 decimal places1.2733 decimal places––––––180 decimal places–––+–––––––0.06–––+2 decimal places51600.076385 decimal places645––––––116.102 decimal placesWrite a zero before the 7 as a placeholder so that the number has 5 decimal places.After you place the decimal point, you can drop any zeros at the end of an answer.ANSWER6.45 18 = 116.1ANSWER1.273 0.06 =CHECKCHECKBecause 6 20 = 120, the product is reasonable.Because 1 = 0.06, the product is reasonable.