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To solve this problem, we will perform vertical addition starting from the rightmost digit:
Therefore, the sum of and is .
1006
\( \begin{aligned} &90 \\ +& \\ &~~9\\ &\underline{\phantom{776}} & \\ \end{aligned} \)
When you add digits and get 10 or more, you write the ones digit below and carry the tens digit to the next column. For example: 9 + 7 = 16, so write 6 and carry the 1.
You start from the ones place (rightmost) because any carries need to go to the next higher place value. Working left to right would mess up your carrying!
If you carry from the highest place value (like hundreds), that carry becomes a new digit! In 689 + 317, the final carry of 1 becomes the thousands digit in 1006.
Try these methods:
Your answer will be too small! In this problem, forgetting carries gives 996 instead of 1006. Always double-check each column for carries ≥ 10.
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