The term ‘carry over’ was taught by my teacher when I was in elementary.
“When you plus 23 and 9 together, 3 + 9 = 12, you write the last digit, ‘2’ and then carry over the digit ‘1’ on top of the digit 2 of 23”
That is basically what I learned back then, and I believe you learned it that way as well.
But, until I got to teach in a learning center using the Singapore curriculum, that’s when I realized “ahh that’s why it works that way”.
In the previous post about Tens and Ones, we learned about value and place value.
In doing vertical method, we have to know that each digit is in the correct place.
First, we need to add the ones.
3 ones + 9 ones = 12 ones.
We can’t write 12 in the ones place because the ones place can only hold one digit. So, we need to rename it. (Learn how to rename here)
12 ones = 1 ten 2 ones.
Now we can put them in their respective places. We put the 1 ten in the tens place, above the 2.
Next, we add the tens together.
1 ten + 2 tens = 3 tens.
Therefore, 23 + 9 = 32.
So what we traditionally call ‘carrying over’ is really a form of renaming.
Happy teaching! I hope math feels a little simpler at home.
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