3.01 Multiplication by single digits
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Knowing your times tables will be helpful in learning other ways to solve multiplication problems.
$9\times7$9×7
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Another word that we can use to describe the ones place is 'units'.
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You might notice that sometimes the standard algorithm is called the 'vertical algorithm'. Let's think about why. When we use the standard algorithm, we line our numbers up in 'vertical' place value columns.
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Let's see how we use the partition, array, and area method to multiply $2$2 digit numbers by $1$1 digit numbers, then see how we could use an algorithm to solve our problem.
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question 1
Let's use the area model to find $66\times3$66×3.
Fill in the areas of each rectangle.
$60$60 $6$6 $2$2 $\editable{}$ $\editable{}$ $1$1 $\editable{}$ $\editable{}$ What is the total area of all four rectangles?
So what is $66\times3$66×3?
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We can also use the strategies we've seen above to multiply larger numbers, so let's see how the area method can be used. Then we solve the same problem, using a standard algorithm. Which do you prefer?
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question 2
Find $7\times785$7×785.
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What if we have larger numbers? Let's see how we can multiply larger numbers by $1$1 digit numbers.
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Question 3
Find $2\times5897$2×5897.
We can use several different methods to solve multiplication problems, but we don't always know if we will need to do any regrouping or trading. If we use an algorithm, regrouping can be done as we solve our problem.