Subtract cm and mm Game

Subtract cm and mm Game
This Subtract cm and mm Game is a subtraction game where you are tasked with finding the remaining length after a “cut” is made. You must know how to borrow from the centimeter column when the millimeters aren’t enough. Scroll down for a detailed explanation.
 

 

How to Play the Subtract cm and mm Game

1. Inspect the Lengths
   You are given a starting length (top row) and the amount to be cut away (bottom row).
   cm: Centimeters
   mm: Millimeters
   

2. The Millimeter Check
   Look at the mm column first.
   If the top number is larger than the bottom number, subtract normally.
   If the top number is smaller, you cannot subtract yet. You must borrow.
   

3. How to “Borrow” a Centimeter
   Since 1 cm = 10 mm, you can trade units to get the millimeters you need.
   Take 1 from the top centimeter box.
   Add 10 to your top millimeter box.
   Now, subtract the millimeters, then subtract the centimeters.
   

Example
Imagine your task is: 12 cm 3 mm minus 5 cm 8 mm
Step 1: The Problem
You can’t take 8 mm from 3 mm.
Step 2: Borrow
Borrow 1 cm from the 12 cm. The top cm becomes 11.
Give those 10 mm to the 3 mm. The top mm becomes 13.
Step 3: Subtract
mm: 13 - 8 = 5 mm
cm: 11 - 5 = 6 cm
Final Answer: 6 cm 5 mm.

This video gives a clear, step-by-step approach on understanding how to subtract mixed units of cm and mm.

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