Unit 3: Fractions

Section 9: Adding and subtracting fractions


Warning! This week looks short.  It does have less different stuff in it than last week's assignments did.  It is an illusion that this is easier.  It's not.  This topic usually takes a full week, because, after doing all this in 1-2 days, students in an in-person will turn in assignments, and I will discover they have missed half of the important ideas.  Then I have to stop the class and redo everything, and make everyone in the class redo everything.  I will do that to you, if you miss stuff the first time around.  Watch and read carefully, think about details, and don't get lulled into a false sense of security because it seems easy.


Writing word problems

A fraction of something: multiplication and recognizing wholes
 How to specify a fractional amount for an addition or subtraction word problem
Subtraction word problems revisited
Analyzing word problems "of" and other things that might go wrong.  An analyzed exampleWord problems to analyze
Do thisAssignment 46: Write addition and subtraction of fractions word problems . (Warning--if you mess up your SRU subtraction word problems, I will insist that you redo them until you get them right)
          thisAsignment 47 D2L Quiz: Analyzing fraction addition and subtraction word problems.


Adding and subtracting with materials:

Watch: Examples of how to explain adding and subtracting fractions with different denominators
Adding with fraction circles
Subtracting with fraction circles
Do thisAssn 48: Adding and subtracting with fraction circles
Instructions for explanation videos about fractions

Adding and subtracting with array pictures or materials

Addition and subtraction with drawn or folded squares showing fractions
Addition and subtraction with rectangles on grid paper showing fractions
Read: My written example of how to explain adding fractions with different denominators
          thisAssn 49:  Record (video) a detailed description of how to add fractions using an array diagram, paying special attention to how the array is formed, and how the equivalent fractions are deduced using multiplication from the array (3/8 + 4/5).
I recommend that you wait until you have feedback on this addition explanation, before doing Assn 50. Email me to get feedback right away.
Do thisAssn 50: Then, do the same thing for a subtraction of fractions problem (7/8 - 2/3).
Instructions for explanation videos about fractions


Adding and subtracting fractions numerically:

with and without a least common denominator

Watch: 3 levels of abstraction in numerical fraction work
Examples with addition
Examples with subtraction

Do thisAssn 51: Choose a fraction addition or subtraction problem where:

Show how compute the sum or difference in all 3 ways I showed. (Pencil and paper work is sufficient--carefully show all steps in your work).