Apply addition and subtraction rules

Key notes:

Addition and Subtraction of Integers

  • Same signs: Add the absolute values and keep the sign.

Example: (−5) + (−3) = −8

  • Different signs: Subtract the smaller absolute value from the larger and take the sign of the larger.

Example: (−7) + 4 = −3

Addition and Subtraction of Fractions

  • Same denominators: Add or subtract the numerators, keep the denominator.

Example: 3/5 + 2/5 = 5/5 = 1

  • Different denominators: Find the least common denominator (LCD), adjust fractions, then add/subtract.

Example: 1/4 + 1/6 = 3/12 + 2/12 = 5/12

Addition and Subtraction of Decimals

  • Align decimal points before adding or subtracting.
  • Use place value to ensure correct calculations.
  • Example: 3.2 + 0.45 = 3.65

Adding and Subtracting Positive and Negative Numbers

  • A negative sign before a number means subtraction.
  • Subtracting a negative number is the same as adding its positive counterpart.
    • Example: 6 − (−3) = 6 + 3 = 9

Order of Operations (BODMAS/PEMDAS)

  • Follow the order: Brackets, Orders (exponents), Division & Multiplication, Addition & Subtraction.
  • Example: 5 + 3 × 2 = 5 + 6 = 11 (Multiplication first)

Applying Addition and Subtraction in Word Problems

Identify keywords:

“Increased by,” “more than” → Addition

“Decreased by,” “less than” → Subtraction

Convert words into equations before solving.

Learn with an example

🎯 The number line shows an unknown number, y.

Is –y positive or negative?

  • positive
  • negative

The unknown number y is to the left of 0. So, y is negative.

The opposite of a negative number is positive. So, –y is positive.

🎯 The number line shows an unknown number, q.

Is q positive or negative?

  • positive
  • negative

The unknown number q is to the right of 0. So, q is positive.

🎯 The number line shows an unknown number, a.

Is a positive or negative?

  • positive
  • negative

The unknown number a is to the right of 0. So, a is positive.

Let’s practice!🖊️