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Chapter 6

Multiply and Divide Decimals. Chapter 6. Lesson 1 – Estimate Products of Whole Numbers and Decimals. Round to the ones place. Example: Estimate 15.8 x 5 15.8 → 16 x 5 → x 5 80 .

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Chapter 6

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  1. Multiply and Divide Decimals Chapter 6

  2. Lesson 1 – Estimate Products of Whole Numbers and Decimals • Round to the ones place. Example: Estimate 15.8 x 5 15.8 → 16 x 5 → x 5 80

  3. Lesson 3 – Multiply Decimals by Whole Numbers • When multiplying a decimal by a whole number, place the decimal point in your answer directly below where it is in the problem. • Examples – 1.) 2 × 0.53 0.53 2.) 12 × 0.7 12 × 2 × 0.7 1.06 8.4

  4. Lesson 5 – Multiply Decimals • When multiplying a decimal by a decimal, move the decimal points all the way to the right to make it a whole number. In your answer, move the decimal point the same number of places to the left. 0.52 52 2 decimal places x 0.6 x 6 + 1 decimal place 312. 3 decimal places 312. = 0.312 – move decimal point 3 places to the left. *If there are no more numbers on the left, you must add zeros.

  5. Lesson 8 – Multiplication Properties • Commutative Property of Multiplication • The order in which the factors are multiplied does not change the product. • Ex. – 5 x 4 = 4 x 5 • Associative Property of Multiplication • The way in which the numbers are grouped does not change the product. • Ex. – (7 x 3) x 9 = 7 x (3 x 9) • Identity Property of Multiplication • The product of any number and 1 equals the number. • Ex. - 12 x 1 = 12

  6. Lesson 9 – Estimate Quotients • Use compatible numbers to divide. Remember, the numbers must go in evenly – no remainders! • Example: $17.50 ÷ 7 → $ 18 ÷ 7 *Does not go in evenly – pick different numbers $21 ÷ 7 = $3 or 14 ÷ 7 = 2

  7. Lesson 11 – Divide Decimals by Whole Numbers • You DO NOT need to use models. The steps are simple. • Write the decimal point in your answer DIRECTLY ABOVE where it is in the problem. ↓ __.__ 3) 4.2 • Divide as you would divide a whole number. _1.4__ 3) 4.2 -3 ↓ 12 -12 0

  8. Lesson 13 – Divide Decimals • Move the decimal point in the divisor to make it a whole number. • Move the decimal point in the dividend the same number of places. • Place the decimal point and divide. _____ ______ o.05) 4.205 → o05.) 420.5 ↑ 2 places ↑ _ 84.1 to the right 5) 420.5 -40↓ 20 -20↓ 05 - 05 0

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