Add and subtract integers: find the sign

key notes:

An integer is a number without a fractional part. Integers can be positive, negative, or zero.

You can add and subtract integers. Read on to learn how!

Adding integers on a number line

You can use a number line to add integers. Follow these steps:

1. Find the first addend on the number line.
2. Add the second addend. To add a positive number, move to the right. To add a negative number, move to the left. The sum is where you land.

Adding a positive integer

Let’s try it. Add –3+5.

Find –3 on the number line. Since 5 is positive, move 5 units to the right.

Since you land on 2, the sum is 2.

So, –3+5=2.

Adding a negative integer

Let’s try another one. Add 4+(–7).

Find 4 on the number line. Since –7 is negative, move 7 units to the left.

Since you land on –3, the sum is –3.

So, 4+(–7)=–3.

Rules for adding integers

You can add integers without number lines. Use the signs of the addends to help you solve!

• If the addends have the same sign, add the absolute values of the addends, and give the sum that sign.
• If the addends have different signs, subtract the lesser absolute value from the greater absolute value, and give the sum the sign of the addend with the greater absolute value.

Adding integers with the same sign

Let’s try it. Add –4+(–6).

The signs of the addends are the same, so add their absolute values.

|–4|+|–6|=4+6=10

Since both addends are negative, the sum is also negative.

So, –4+(–6)=–10.

Adding integers with different signs

Let’s try another one. Add –4+6.

The signs of the addends are different, so subtract the lesser absolute value from the greater absolute value.

|6|–|–4|=6–4=2

Since the positive addend, 6, has a greater absolute value, the sum is positive.

So, –4+6=2.

Learn with an example

let’s practice: