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To solve this problem, we will use the vertical addition method:
The sum of and is .
Therefore, the correct answer is .
810
\( \begin{aligned} &90 \\ +& \\ &~~9\\ &\underline{\phantom{776}} & \\ \end{aligned} \)
We start from the ones place (rightmost) because carrying moves left! If we started left, we'd have to go back and change our work when we carry. Starting right ensures we handle all carrying as we go.
Your final answer will be too small! For example, if you forget to carry the 1 from , you might get 800 instead of 810. Always double-check your carrying.
Yes, but vertical addition is more organized and reduces errors! It keeps place values aligned and makes carrying easier to track. Horizontal addition works for small numbers but gets confusing with larger ones.
Check each column: if the sum is 10 or more, you must carry. Write the ones digit below and carry the tens digit left. For , write 1 and carry 1.
The same rules apply! Add all digits in each column, carry when needed. With practice, you can add multiple numbers just as easily as two numbers.
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