Integer addition and subtraction rules

Key Points:

  • If you add two positive numbers, the result is positive.
    • Ex: 25 + 8 = 33
  • If you add two negative numbers, the result is negative.
    • Ex: -5 + -15 = -20

When you add a positive number and a negative number:

  • If the positive number has a bigger magnitude, the result is positive.
    • Ex: 25+ -8 = 17
  • If the negative number has a bigger magnitude, the result is negative.
    • Ex: 2 + -67 = -65

Points to remember

  • Adding a negative is the same as subtracting a positive.
    • 5 + -2 = 3 –> 5 – 2 =3
  • Subtracting a positive is the same as adding a negative.
    • -5 − 1 =-6  –> -5 +-1 =-6
  • Subtracting a negative is the same as adding a positive.
    • 2 − -4 =6   –> 2 + 4 = 6

Learn with an example

➡️ Is -17 + -20 positive or negative?

  • positive
  • negative

When you add two negative numbers, like -17 and -20, the result is negative.

You can check your answer by doing the maths.

-17 + -20 = -37

👉As you can see, the result is negative.

➡️ Is 48 − 9 positive or negative?

  • positive
  • negative

Since you are subtracting a smaller positive number, 9, from a larger positive number, 48, the result remains positive.

You can check your answer by doing the maths.

48 − 9 = 39

👉As you can see, the result is positive.

➡️ Is -4 + 18 positive or negative?

  • positive
  • negative

When you add a negative number, –4, and a positive number, 18, the result has the same sign as the number with the larger magnitude.

The magnitude of -4 is 4.

The magnitude of 18 is 18.

Since 18 has a larger magnitude and 18 is positive, the result is positive.

You can check your answer by doing the maths.

-4 + 18 = 14

👉As you can see, the result is positive.

Let’s practice!🖊️