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Look at how Benjamin added 32 to 27 by adding three tens and then two ones.
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Use number lines to find the answers to these sums, 43 plus 32, and then 67 plus 14.
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Before we calculate the answer to those sums, let’s go back and look at how Benjamin has used the number line to help him find the answer to his addition.
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Benjamin is adding 32 to 27.
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This means that he starts with the number 27, and then adds 32 onto it.
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This is why his number line begins with the number 27.
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Instead of adding 32 all in one go, Benjamin partitions the number 32 into tens and ones.
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We can split 32 into 30 and two, which is the same as adding three tens and two ones.
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And that’s why these are the jumps that Benjamin makes on his number line.
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First, he adds three tens.
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So, he starts at 27 and counts on in tens three times, 37, 47.
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And then, from 57, he adds two ones, 58, 59.
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So, that’s how he arrives at the answer 59.
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Let’s use number lines in a similar way to find the answers to the sums.
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Firstly, 43 plus 32.
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We start with the number 43.
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And then, we need to partition 32 into tens and ones.
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32 is three tens and two ones, as we’ve seen already.
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So, we need to make three jumps of 10 and two jumps of one.
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Let’s count in tens from 43, 43, 53, 63, and 73.
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Now let’s add the two ones, starting with 73, 74, 75.
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And so, by adding three tens and two ones, we found that 43 plus 32 equals 75.
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Let’s use the same method to calculate 67 plus 14.
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Start with the number 67.
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Partition the number 14 into one ten and four ones.
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Count on one ten, 67, 77.
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And then, add our four ones, 78, 79, 80, and 81.
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And so, by adding one ten and four ones, we found that 67 plus 14 equals 81.