The problems presented for addition/subtraction with like denominators are word problems using familiar objects in which the denominators are not given but need to be supplied from the context of the problem – just like we have to do in real life. If we need to know a fraction of a dozen, the denominator is 12...of an hour, 60...;of a day, 24...of a dollar, 100...and so on.
These activities do not give a basic introduction to addition/subtraction of fractions with like denominators. That is fairly simple to do with objects, shading, number lines (Fraction Towers), etc.
These activities do go through the process of adding/subtracting fractions with unlike denominators from the start, beginning with a quick review of writing equal fractions and identifying multiples, and then finding common multiples and the Least Common Multiple.
There is a simple format and process with which students can get used to the several-step process of identifying the LCM, writing equal fractions, and performing the addition or subtraction. Problems in which one denominator is the LCM are presented along with problems requiring the identifying of a new LCM.
Common Core Standards:
4.NF.3.d: “Solve word problems involving addition and subtraction of fractions referring to the same whole and having like denominators....”
5.NF.1: “Add and subtract fractions with unlike denominators ...by replacing given fractions with equivalent fractions in such a way as to produce an equivalent sum or difference of fractions with like denominators.”
Subject: Math, Fractions, Word problems
Level: Grades 4 – 5
Length/Duration: 15 pages of student work, 3-4 days if done consecutively
A Smart Notebook 10 file is also included.