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Door 1 · Grade 7

🔢 Rational Numbers

Positive + Positive = Positive

▶ Play Door 1

Adding & Subtracting Positive and Negative Integers

Integers are whole numbers that can be positive (+), negative (-), or zero. Think of a number line as your main tool for visualizing integer operations.
Rules for addition:
• Same sign: add absolute values and keep the sign. Example: (-3) + (-4) = -7
• Different signs: subtract absolute values and keep the sign of the number with the larger absolute value. Example: (-8) + (+3) = -5

Rule for subtraction: Subtracting a number is the same as adding its opposite.
Example: 5 - (-3) = 5 + 3 = 8
RuleExampleResultPositive + Positive4 + 5+9Negative + Negative(-4) + (-5)-9Different signs(-8) + 3-5Subtraction rule5 - (-3)8

Worked example

Problem: A scuba diver is at -12 feet. She rises 7 feet. Where is she now?

  1. -12 + 7 = -5 feet (still below sea level)

Answer: -12 + 7 = -5 feet (still below sea level)