Need help solving mixed number subtraction problems like 3 ⅗ - 1 ⅕ ? This post (and video!) will guide you through THREE simple strategies to make subtracting mixed numbers a breeze for upper elementary students. We'll explore number lines, visual models, and equations, so you can find the method that works best for your learning style.
Watch the Video:
Why Subtract Mixed Numbers?
Before we dive into the how, let's talk about the why. Subtracting mixed numbers is a practical skill that pops up in real-life situations more often than you might think!
Leftover Pizza: Figuring out how much pizza is left after a party.
Home Renovation: Calculating the length of wood needed for a project after some has been cut off.
Measuring Workouts: Tracking the distance covered during different parts of an exercise routine.
3 Strategies for Subtracting Mixed Numbers
Ready to tackle those mixed numbers? Let's explore three effective strategies:
1. Number Line Subtraction
Visual learners, this one's for you! A number line helps you see the difference between two mixed numbers.
Plot the Numbers: Mark both mixed numbers on a number line.
Find the Distance: Count the spaces between the two numbers to find the difference.
Tip: To make sure your whole number jumps are correct, think of the fraction equivalent to one whole (e.g., 5/5 = 1).
2. Subtracting with Models
Models provide a concrete way to visualize subtraction.
Represent the First Number: Draw a picture to represent the first mixed number (e.g., circles for whole numbers and divided sections for fractions).
Take Away: Cross out the amount represented by the second mixed number.
Count What's Left: The remaining parts represent your answer.
3. Using Equations
This is the standard algorithm for subtracting mixed numbers:
Line Up: Write the problem vertically, aligning whole numbers with whole numbers and fractions with fractions.
Subtract Fractions: Subtract the numerators of the fractions, keeping the denominator the same.
Subtract Whole Numbers: Subtract the whole numbers.
(Future Lesson!) Regrouping: If the top fraction is smaller than the bottom fraction, you'll need to regroup (borrow) from the whole number. We'll cover that in another video!
Learning Standards Connection:
This video aligns with the following Common Core standards:
4.NF.B.3c: Add and subtract mixed numbers with like denominators.
Let's make subtracting mixed numbers a piece of cake (or pizza)!
What strategy works best for you and your students? I found that having multiple strategies gives each students the choice to find one that works best for them!
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