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Adding Decimals

The Hook

Dealing with pocket change.

What is it?

Adding numbers that have parts less than one.

Time Travel (History)

Simon Stevin introduced the decimal system to Europe in 1585.

Cheat Code

Button up your shirt: Keep the decimal buttons (points) in a straight vertical line.

Practice This Now!

The Field Guide

In Plain English: Adding decimals is exactly like adding big numbers, but you MUST line up the dots. If one number has no dot, it goes at the end.

In The Real World: Adding $10 (no cents) and $2.50. You must add the 2 to the 0, not the 1.

How To Do It

  1. Write the numbers vertically.
  2. LINE UP THE DOTS.
  3. Fill empty spaces with 0.
  4. Add normally.
⚠

Booby Trap!

Lining up the last number instead of the dot.

Real World Challenge
"You have 1.5 liters of soda and buy a 2 liter bottle. How much soda total?"
The Logic: 1.5 + 2.0 = 3.5 Liters. (Line up the 1 and the 2).

Training Drills

The Line Up
3.14 + 2.50 ------ 5.64
Dots are straight.
Whole Numbers
12.0 + 0.5 ------ 12.5
12 becomes 12.0