Lesson 3: Add Integers

Property

To add integers with the same sign, add their absolute values and keep the common sign.

To add integers with different signs, subtract the smaller absolute value from the larger absolute value. The sum has the sign of the number with the larger absolute value.

Examples

• To add $-15 + (-8)$, the signs are the same. Add $15 + 8 = 23$ and keep the negative sign, so the sum is $-23$.
• To add $-10 + 25$, the signs are different. Subtract $25 - 10 = 15$. Since $25$ has the larger absolute value, the result is positive: $15$.
• To add $12 + (-30)$, the signs are different. Subtract $30 - 12 = 18$. Since $-30$ has the larger absolute value, the result is negative: $-18$.

Property

The Additive Inverse Property states that the sum of any integer and its opposite is always zero. An integer and its opposite are called additive inverses.