## Integers

The integers are the positive and negative whole numbers and include zero.

I = {...-4, -3, -2, -1, 0, 1, 2, 3, 4...}

Use a number line when adding and subtracting integers. The first integer is the starting point on the number line.

• When adding a positive integer, move to the right.

e.g. 4 + 2 = 6 • When adding a negative integer, move to the left.

e.g. 4 + − 2 = 2 Subtraction

• When subtracting a positive integer, move to the left.

e.g. 4 − 2 = 2 • When subtracting a negative integer, move to the right.

e.g. 4 − − 2 = 6 Multiplication and division

The rule is the same for both multiplying and dividing two integers.

• If the signs of the two integers are the same, the answer is positive.
• If the signs of the two integers are different, the answer is negative.

The table illustrates these rules:

 ×/÷ +ve −ve +ve + − -ve − +

Examples:

 For multiplication For division 5 × 2 = 10 5 ÷ 2 = 2.5 - 5 × − 2 = 10 - 5 ÷ − 2 = 2.5 5 × − 2 = -10 5 ÷ − 2 = − 2.5 - 5 × 2 = − 10 - 5 ÷ 2 = − 2.5

For practice with integer calculations − 