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5-Minute Check•Multiply.
•2 x 44
•4 x 39
•3 x $21
•5 x 89
•A truck weighs twice as heavy as a car. The car weighs 3,000 pounds. How much does the truck weigh?
Multiply Multi-Digit Numbers (even across zeros)
ObjectiveBy the end of the lesson, you will be
able to multiply a three-digit and a four-digit number by a one-digit number.
Standard 4NS3.2 - Demonstrate an understanding of, and the ability to use, standard algorithms for multiplying a multidigit number by a two-digit number and for dividing a multidigit number by a one-digit number; use relationships between them to simplify computations and to check results.
Introduce Let’s look at a problem: 1, 124
x3
• How many ones are in 1,124?
• Multiply the ones by the 3. What is the product? Should we carry over?
• Multiply the tens. What is the product? Should we carry over any?
• Multiply the hundreds. What is the product? Should we carry over?
• Multiply the thousands. What is the product?
• What is the final answer?
Example• Today is Anna’s birthday, and she is nine years
old. There are 365 days in one year. How many days old is Anna?
• You multiply multi-digit numbers the same way you multiply a two-digit number by a one-digit number.
• 365
x9
First, multiply the 9 by 5. Anything to carry over?
Next, multiply the 9 by the 6 (tens) and add the carried-over amount. Anything to carry over?
Then, multiply the 9 by the 3 (hundreds) and add the carried-over amount.
LET”S LISTEN!!•Let’s hear from Mrs. Verughese about multiplying money using four-digit by one-digit.
•Mrs. Verughese!!
•Let’s listen to Mr. Parsons as he explains another problem with a zero as one of the digits.
•Mr. Parsons!!
Teach• Let’s look at a problem that has a zero in it:
• 1,104
x3
• How many ones are in 1,104? Multiply the ones by 3. What is the product? Anything to carry over?
• How many tens are in 1,104? What is the product of any number and zero? Then, add the carried over amount. Anything to carry over?
• Multiply the hundreds. What is the product? Anything to carry over?
• Multiply the thousands. What is the product? Add the carried over amount.
Bales Bucks
Multiply. Check for reasonableness by estimating the products.
303 x 3
$507 x 6
908 x 8
2,007 x 8
8 x 47
Multiply. Check for reasonableness.
135 x 2
532 x 6
$2,957 x 3
7,832 x 7
Assignment
Page 280 - #’s 7 – 12
Page 286 - #’s 9 - 15
Get them all correct – No Math Homework