Integers and Signed-Number Reasoning
Interpret signs as direction and position, then solve multi-step integer problems without losing meaning in mechanical sign rules.
Integers
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A sign describes position or direction
Positive and negative values often describe opposite directions: above and below, deposit and withdrawal, gain and loss, rise and fall. Keep that meaning visible while calculating.
Change = final−initialDistance between a and b: |a−b|An even number of negative factors gives a positive product; an odd number gives a negative product.Addition
Same signs: add magnitudes and keep the sign. Different signs: subtract magnitudes and keep the sign of the larger magnitude.
Subtraction
Rewrite a−b as a + (−b), then use addition reasoning.
Multiplication and division
Same signs give positive; different signs give negative.
Absolute value
|x| is distance from zero, so it is never negative.
Direction first, arithmetic second
1. Name zero or the reference level.
2. Translate each change: risedeposit/gain is positive; fallwithdrawal/loss is negative.
3. Combine in chronological order.
4. Interpret the final sign. A negative result may be a valid debt, depth, or below-zero temperature.
Why it works
Students often perform the arithmetic correctly but attach the wrong sign because they stopped tracking what the sign represents.
Five forms you should recognize
Removing a negative has the same effect as adding its positive opposite.
Distance is nonnegative even when one location is negative.
Crossing zero means the change is larger than either endpoint’s magnitude alone.
Each upward or downward movement is entered with its direction.
Three negative factors give a negative product because the number of negative factors is odd.
Check before you commit
- Thinking the integer with the larger magnitude is always greater
- Treating subtraction of a negative as subtraction of its magnitude
- Forgetting parentheses around a negative base with an exponent
- Reporting a negative distance
- Dropping the initial signed value in a change problem
- Assuming every negative result is an error
Do you need the lesson-or just practice?
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Foundations
Build the core procedure with immediate explanations.
Core Practice
Use mixed forms with less scaffolding.
UPCAT-Style Transfer
Apply the competency in unfamiliar representations.
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Integers and Signed-Number Reasoning FAQ
Why is −2 greater than −9?
−2 lies farther right on the number line and is closer to zero.
Is (−3)² the same as −3²?
No. (−3)² = 9, while −3² means −(3²) = −9 under standard order of operations.
When should I use absolute value?
Use it for distance or magnitude when direction does not matter.
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