Operations with Integers

Overview

Integers include positive numbers, negative numbers and zero. This chapter shows how to add, subtract, multiply and divide integers using the number line and sign rules.

Key concepts

• Integers: ..., −3, −2, −1, 0, 1, 2, 3, ...
• Adding a negative is the same as subtracting.
• Sign rules for multiplication and division.
• The number line helps visualise movement.

Important formulae

• (+) × (+) = (+); (−) × (−) = (+)
• (+) × (−) = (−); (−) × (+) = (−)
• a − b = a + (−b)

Solved example

1. Find (−6) × (−4).
2. Negative times negative gives positive.
3. So (−6) × (−4) = 24.

Important questions

1. Compute (−8) + 5.
2. Find 7 − (−3).
3. Evaluate (−12) ÷ 4.
4. Find (−2) × 3 × (−5).

Quick revision

Same signs multiply/divide to a positive; different signs give a negative. Subtracting a number means adding its opposite. The number line keeps directions clear.