Subtraction is taking an amount away from another amount. The steps outlined will help keep you organized as we start subtracting numbers too big to do in your head.
Steps for Subtraction:
- Place the biggest number on top.
- Stack in columns according to place value.
- Regroup when needed.
- Subtract in columns by place value starting on the right and going left.
- The strongest wins. (If the bigger number was negative then the answer is negative. If the bigger number was positive then the answer is positive.)
The following videos introduce the concept of subtraction, then explain what it means to subtract with negative numbers:
Video Source (02:17 mins) | Transcript
Video Source (03:22 mins) | Transcript
Video Source (03:03 mins) | Transcript
Subtraction is the same as adding, but going in the opposite direction. On a number line, we add going to the right. When we subtract, we go to the left.
\(5 - 4 = 1\) looks like this on the number line. We start at \(5\) and move to the left \(4\) spaces ending at \(1\).
This is the same as \(5 + (-4) = 1\)
Video Source (04:39 mins) | Transcript
Examples: \(5 - 4\) does not equal \(4 - 5\)
\(5 + (-4) = (-4) + 5\)
Video Source (05:58 mins) | Transcript
When we talk about the strongest number, we mean the number that is furthest from \(0\) in either the positive or negative direction. It is the biggest number regardless of its sign.
- Khan Academy: Basic Subtraction (08:31 mins, Transcript)
- Khan Academy: Subtracting Different Ways (12:31 mins, Transcript)
- Khan Academy: Subtracting with Regrouping (05:26 mins, Transcript)
Practice ProblemsEvaluate the following expression:
- \(9 - 7\) = ? (Solution
- \(8 - 4\) = ? (Solution
- \(11 - 8\) = ? (Video Solution
- \(10 - 2\) = ? (Video Solution
- \(17 - 8\) = ? (Solution
- \(11 - 9\) = ? (Solution
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