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Created by Shaunak Ghosh
You will learn to neatly line up big numbers, then fluently add and subtract multi-digit whole numbers using the standard algorithm. You will also solve word problems by choosing the correct operation, setting up the problem, and checking that your answer makes sense.
7 modules • Each builds on the previous one
Before you add or subtract, you must stack numbers so ones are under ones, tens under tens, and so on. This keeps every digit in the correct place so your answer makes sense.
Use the standard algorithm to add whole numbers up to 999,999. Add from right to left (ones to highest place), writing each digit in the correct column.
Sometimes a column adds to 10 or more. You write the ones digit and “carry” the tens to the next column to the left.
Solve story problems that mean “put together” or “total.” First decide what the problem is asking, then add using the standard algorithm.
Use the standard algorithm to subtract multi-digit numbers up to 999,999. When the top digit is smaller, regroup (borrow) from the next place to the left.
Sometimes you need to regroup across one or more zeros (like 50,002 − 1,876). You may need to “borrow” from farther left and turn zeros into 9s.
Solve story problems that mean “take away,” “how many left,” or “find the difference.” Decide if subtraction is needed, then subtract using the standard algorithm and check your answer.
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In-video quizzes and scaffolded content to maximize retention.