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Dividing Decimals

Overview

Moving the wall.

What is it?

How to handle a decimal point in the divisor.

History

Crucial for scientific measurements.

Key Idea

Move the decimal in the OUTSIDE number to the right until it's whole. Do the same to the inside.

Practice This Topic

Concept Guide

Plain English: We hate dividing by decimals (like 1.5). We prefer whole numbers. So we multiply both numbers by 10 (move the dot) until the outside number is clean.

Real-world example: Figuring out how many $0.25 gumballs you can buy with $5.00.

How to do it

  1. Look at the Divisor (Outside).
  2. Move dot right until it's a whole number.
  3. Move the Dividend (Inside) dot the SAME number of jumps.
  4. Raise the roof (put dot straight up in answer).
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Common Pitfall

Moving the dot on the outside but forgetting to move it on the inside.

Word Problem
"A plank is 1.5 meters. You have 4.5 meters of wood. How many planks?"
Reasoning: 4.5 ÷ 1.5 -> Move dots -> 45 ÷ 15 = 3 planks.

Practice Examples

The Slide
1.2 | 3.6 becomes 12 | 36
Moved dot 1 time.