2. Adding & Subtracting Fractions
Teacher Notes:
• Use This presentation to teach the steps for adding
and subtracting fraction with unlike denominators.
• Two assumptions are being made before students
engage in this lesson: 1) they know how to add
fractions with like denominators, and 2) they know
how to write equivalent fractions.
3. Overview / Goal
At the conclusion of this lesson students will be able to:
- Change fractions so they have the same denominators
- Add or subtract fractions
- Write the answer in simplest form
4. Instructions
• • Recall prior knowledge of basic adding and subtracting skills
•
• • Recall prior knowledge of single and two digit division skills
•
• • Preview a video that shows how to add and subtract fractions
• • Whole class discussion to test for understanding
•
• • Complete a 3 x 6 matrix by writing equivalent
•
• • Give feedback
•
• • Compare Tangram figures and describe 3 similarities
5. Basic Math Skills: Adding and Subtracting Fractions
www.YouTube.com/watch?v=VzCgaKu-pMw
6. REVIEW WHAT YOU JUST LEARNED FROM THE VIDEO
What are some of the strategies used for adding and subtracting fractions
with unlike denominators?
– a. Add both of the numerators together and then add both of the
denominators true ______ or false _______
– b. Change the fractions so that the denominators are the same, then add or
subtract as indicated true ______ or false ________
– c. Remove the plus and the negative signs and multiply the numerators,
then multiply the denominators true _____ or _____ false
– d. Change the denominators to any number, as long as they are both the
same and add the top numbers only true _____ or false ______
7. GUIDED PRACTICE
1. Given a 3 x 6 matrix write an equivalent fractions in the horizontal
blank spaces, adjacent to the given fractions.
2. You will show understanding of the concept by getting 75% of the
problems correct.
8.
9. A
B
C D
Name each figure by what it appears to be.
On the next page describe three similarities.
10. Describe three similarities about the Tangram Figures
1. ______________________________________________________
_________________________________________________________
2. _______________________________________________________
_________________________________________________________
3. _______________________________________________________
_________________________________________________________
11. SUMMARY OF ACTIVITY
You will show your understanding of the concept by getting 9 of 12
questions correct (75%) on the fraction matrix
What did you not learn about adding and subtracting fractions and
writing the answers in simplest form?
What did you learn?
Extension to Activity (Homework)
Explore writing equivalent fractions where the numerator and the
denominator are not multiples of each other. This should be used as
a homework investigation where students investigate different ways
to compare these type of fractions, i.e. 3/6 = 7/14.
12. REFERENCES
Burns, M. (1992) About Teaching Mathematics (A K-8 Resource)
(2nd ed.) White Plains, N.Y., Burns Ed and Associates
Hiebert, J., Carpenter, T., Fennema, E., Fusion, K., Wearne, D., Murray, H.,
Oliver, A., and Human, P. (1997) – Making Sense -Teaching and Learning
Mathematics with Understanding (1st ed.), Portsmith, NH, University of
Wisconsin.
Rabin, J., & Brookins, B. (1999/2000), Algebra Thinking Institute (ATI) at
University of California, San Diego (UCSD)
