Chapter 9 · Questions · page 39 of 68
How do you add negative numbers?
Short answerIf the signs match, add the sizes and keep the sign. If they differ, subtract the smaller size from the larger and keep the sign of the larger one.
levelPre-algebra
standard7.NS.A.1
practiceInteger operations
Picture a number line. Adding a positive number moves you right, adding a negative moves you left. So -8 + 5 starts at -8 and moves 5 to the right, landing on -3.
How to use it
- Look at the two signs.
- Same signs: add the sizes, and the answer keeps that sign.
- Different signs: subtract the smaller size from the larger, and the answer takes the sign of the number that was larger in size.
Example
Where it goes wrong
- Thinking two negatives added make a positive. That rule is for multiplying.
- Keeping the sign of the first number instead of the larger one.