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5 Minute Math Place the following decimal numbers in increasing order: How many tens are in each of the following numbers: 15,330 12.389 12.39 3,922 12 447 12. 398 Multiplying a Decimal by a Natural Number Multiplying by 10, 100, 1000 3.4 Learning Goal We will use our prior understanding of multiplying two natural numbers so that we can multiply a decimal number by a natural number. We’ll know we’ve got it when we can correctly multiply decimal numbers by natural numbers. Vocabulary • • • • Decimal Factor Hundredth Multiplication • • • • Place Product Tenth Thousandth Multiplying a Decimal Number by a Natural Number Steps Example: 26.2 x 3 1. Remove the decimal from the first factor and arrange the numbers in rows. 262 x 3 ---------- 2. Multiply the 2 numbers as if they were natural numbers. 262 x 3 ---------786 3. Count the number of digits after the decimal point in the 1st factor. 26.2 There is 1 digit after the decimal point. 4. Place a decimal point in the product, keeping the same number of digits after the decimal point. 26.2 x 3 ---------78.6 Multiplying a Decimal Number by a Natural Number Steps Example: 428.74 x 36 1. Remove the decimal from the first factor and arrange the numbers in rows. 42874 x 36 ---------- 2. Multiply the 2 numbers as if they were natural numbers. 42874 x 36 ---------1543464 3. Count the number of digits after the decimal point in the 1st factor. 26.2 There is 1 digit after the decimal point. 4. Place a decimal point in the product, keeping the same number of digits after the decimal point. 428.74 x 36 ---------15434.64 Multiplying by 10, 100, 1000 • When multiplying a decimal number by 10, 100 or 1000, simply move the decimal place to the right • The number of zeroes in the 2nd factor (10, 100, 1000) will indicate how many places to move the decimal and add zeroes to the end of the product as needed Multiplying by 10, 100, 1000 • 1928.322 x 10 • 228.7 x 100 • 109.83 x 1000 Let’s Practice Grade 5 • Page 102 Grade 6 • Page 103 – #1 a, b – #3 a, b – #1 a, b – #3 • Page 103 • Page 105 – #1 a, b, c – #2 a, b, c – #4 – #1 – #3 – #4 a, c, e