Negative Numbers — Full Operations

Negative × negative = positive. Why? Taking away a debt is a gain. The number line visualizes. Indirect aim: algebra fluency, preparation for equations.

• Framework: Montessori
• Unit: Mathematics
• Learning area: Algebra
• Level: Ages 8-10

Objectives

• Perform add, subtract, multiply, divide with negatives
• Apply sign rules consistently
• Solve word problems with negatives
• Use number line for visualization

Materials

• Number line
• Peg board with red/green
• Problem slips
• Worked examples

Instructions

1. Addition: -3 + 5 = 2 (move right from -3). 2. -3 + (-5) = -8 (move left). 3. Subtraction: 3 - (-5) = 3 + 5 = 8. 4. Multiplication signs: (+)(+)=+; (-)(-)=+; (+)(-)=-. 5. (-3)(-4) = 12 (taking away -3 four times = +12). 6. Division: same signs. (-12)÷(-4) = 3. 7. Word problems: temperature drops, debt. 8. Verify with number line or peg board.

Educator tip

The (-)(-)=+ rule is the trickiest. Use debt analogy: 'removing debt' = gaining money.

Assessment

Observe correct sign application, word problem setup, and verification.

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