3.08 Multiplication with up to 2 digits
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We can multiply numbers by larger numbers, once we've mastered multiplying by single digit numbers.
Find $5296\times4$5296×4.
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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 to multiply a $2$2 digit number by another $2$2 digit number.
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Question 1
Let's use the area model to find $28\times55$28×55.
Fill in the areas of each rectangle.
$25$25 $3$3 $50$50 $\editable{}$ $\editable{}$ $5$5 $\editable{}$ $\editable{}$ Find the sums of each column
$25$25 $3$3 $50$50 $1250$1250 $150$150 $5$5 $125$125 $15$15 Total: $\editable{}$ $\editable{}$ What is the total area of the rectangles?
$25$25 $3$3 $55$55 $1375$1375 $165$165 So what is $28\times55$28×55?
Using a standard algorithm means we can multiply larger numbers the same way, just with more steps. Once we know how to solve problems this way, there's no limit to how big the numbers could be!