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Integers & Number Line

The Hook

Positive, Negative, and Zero.

What is it?

The set of whole numbers and their opposites (..., -2, -1, 0, 1, 2, ...).

Time Travel (History)

Negative numbers were once considered 'absurd' or 'false' numbers until the 17th century.

Cheat Code

Subtracting a negative is the same as Adding a positive (Two wrongs make a right).

Practice This Now!

The Field Guide

In Plain English: Numbers don't stop at zero. Integers are like elevation: Positive is the mountain (Up), Negative is the ocean (Down). Zero is sea level. The 'bigger' a negative number looks, the smaller it actually is.

In The Real World: Golf scores (Under par), Temperature (-5 degrees), Debt (Negative money).

How To Do It

  1. Adding Same Signs: Add the numbers, keep the sign (-5 + -2 = -7).
  2. Adding Different Signs: Ignore signs, subtract smaller from bigger. Keep the sign of the 'heavier' number (-10 + 3 -> 7, negative wins -> -7).
  3. Subtracting: Change 'Minus' to 'Plus Negative' and follow addition rules.
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Booby Trap!

Thinking -10 is bigger than -2 because 10 > 2. Wrong. -10 is 'more debt' or 'colder', so it is smaller.

Real World Challenge
"You are on the 3rd floor. You go down 5 floors. Where are you?"
The Logic: Start at +3. Down means minus. 3 - 5. Difference is 2. The negative move was bigger. Answer: -2 (Basement Level 2).

Training Drills

Double Negative
5 - (-2) = 7
Minus-Minus becomes Plus.