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Subtracting Negatives

Overview

The Double Negative.

What is it?

Removing a debt, which is the same as gaining value.

History

One of the hardest concepts to visualize, used extensively in accounting.

Key Idea

Minus a Minus equals a Plus. (The two lines come together to make a +).

Practice This Topic

Concept Guide

Plain English: Think of a negative number as 'Cold Air'. If you Subtract (remove) Cold Air from a room, the room gets Warmer (Positive). Subtracting a negative is adding.

Real-world example: Debt forgiveness. If the bank 'subtracts' your debt, your net worth goes UP.

How to do it

  1. Spot the double signs: 5 - (-3).
  2. Connect the two dashes to make a plus sign (+).
  3. Rewrite as addition: 5 + 3.
  4. Solve.
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Common Pitfall

Keeping it negative. 5 - (-3) is NOT 2. It is 8.

Word Problem
"You are at -10 feet (underwater). You subtract -5 feet (you go up). Where are you?"
Reasoning: -10 - (-5) becomes -10 + 5. You are now at -5 feet.

Practice Examples

The Switch
7 - (-2) becomes 7 + 2 = 9
Minus Minus = Plus.