Operations with Integers

Adding, subtracting, multiplying and dividing negative numbers, and the sign rules that make it work.

Key ideas

• On the number line, numbers increase to the right: −5 is less than −2.
• Subtracting a number is the same as adding its opposite: 4 − (−3) = 4 + 3 = 7.
• Multiplying or dividing two numbers with the same sign gives a positive answer; different signs give a negative answer.
• A product of several numbers is negative when an odd number of them are negative.
• Zero times any integer is 0; division by 0 is not defined.

Remember

Watch out

• Saying −5 is bigger than −2.
• Forgetting that minus a negative becomes plus.
• Counting the signs wrong when multiplying three or more negatives.

Worked example