1. Chapter 7
ADD & SUBTRACT FRACTIONS WITH
UNLIKE DENOMINATORS

2. CHAPTER 7 VOCABULARY
 Least Common Multiple (LCM) – the smallest
number that is a multiple of two or more
numbers
 Least Common Denominator (LCD) – is the
LCM of two or more denominators

3. BRAIN POP VIDEO
 Adding & Subtracting Fractions

4. Investigate
Materials needed: fractions strips
Draw Conclusions
1. Describe how you would
determine what fraction strips,
all with the same denominator,
would fit ½ + 1/3
2. Explain how finding strips with
the same denominator for ½ +
1/3 and ½ + ¼ are different.
7.1 ADDITION WITH UNLIKE DENOMINATORS

5. CONNECT PG. 288

6. PROBLEM SOLVING PG. 290

7. 7.1 MATH JOURNAL QUESTION
How can you use models to add
fractions that do not have the
same denominator?

8. Investigate
Materials: Fraction strips
Draw Conclusion:
1. Describe how you determined
what fraction strips , all with the
same denominator, would fit
exactly under the difference?
2. Explain whether you could have
used fraction strips of any other
denominator to find the
difference, if so, what is the
denominator?
7.2 SUBTRACTION WITH UNLIKE DENOMINATORS

9. CONNECT PG. 292
Sometimes you can use different sets of same-denominator fraction strips
to find the difference. All of the answers will be correct.

10. SHARE & SHOW (EXTRA PRACTICE)

11. UNLOCK THE PROBLEM (TEST PREP) PG. 294

12. 7.2 MATH JOURNAL QUESTION

13. 7.3 ESTIMATE FRACTION SUMS & DIFFERENCES
 One way – benchmark numbers 0, ½, 1
 Use benchmark numbers to estimate the
following fractions:
4/6
1/8
3/5
7/8

14. UNLOCK THE PROBLEM PG. 295

15. ANOTHER WAY PG. 296 (MENTAL MATH)

16. TRY THIS! ESTIMATE (PG.296)

17. PROBLEM SOLVING PG. 298 (17-19 & 21)

18. 7.3 MATH JOURNAL QUESTION

19. 7.4 LEAST COMMON MULTIPLE
 One way: make a list
 Start by making a list of the first 5 multiples of
each number (you may have to find more than the first 5
depending on the numbers). Underline the common
multiples of the numbers. Circle the LCM of
the numbers.
Example: 6: 6, 12, 18, 24, 30, 36, 42, 48
8: 8, 16, 24, 32, 40, 48, 56, 64
LCM of 6 & 8 is 24.

20. ANOTHER WAY – USE PRIME FACTORIZATION
 What numbers are prime
factors of either 6 or 8?
 The prime factor 2 occurs
most often in the prime
factorization of ___.
 Write each prime factor the
greatest number of times it
appears in one factor tree.
Multiply.
 2 x 2 x 2 x 3 = 24
 LCM is 24.

21. LEAST COMMON DENOMINATOR PG. 300
 Step 1: find the least
common multiple of
both denominators.
 Step 2: use the LCM as
the LCD and create
equivalent fractions.
***important information***
Whatever you do to the
denominator you must do the
same to the numerator!

22. SHARE & SHOW (EXTRA PRACTICE) FIND THE LCM
 3&5
3&9
 9 & 15
Find the LCD & then write an equivalent fraction
3&1 5&1 1&1
5 4 8 5 12 2

23. UNLOCK THE PROBLEM & WORD PROBLEMS
PG. 302

24. 7.4 MATH JOURNAL QUESTION
Howcan you find the least
common multiples and least
common denominators?

25. 7.5 STRATEGIES TO FIND THE LCD

26. ACTIVITY PG. 304

27. TRY THIS! PG. 304

28. PROBLEM SOLVING PG. 306

29. 7.5 MATH JOURNAL QUESTION
What are some helpful strategies
for finding the LCD of pairs of
fractions?

30. ONE WAY – USE A COMMON
DENOMINATOR ANOTHER WAY – USE THE LCD
7.6 USE COMMON DENOMINATORS

31. Explain how you know
whether your answer is
reasonable.
EXAMPLE PG. 308

32. 26. Sara is making a key chain,
using the bead design shown.
What fraction of the beads in
her design are either blue or
red?
Use the picture for 26 – 27. 27. In making the key chains,
Sara uses the pattern of
beads 3 times. After the key
chain is complete, what
fraction of the total beads are
either white or blue.
PROBLEM SOLVING PG. 310

33. 7.6 MATH JOURNAL QUESTION

34. MID – CHAPTER REVIEW

35. Step 1: Estimate the sum
Step 2: Find a common denominator.
Use the common denominator to
write equivalent fractions with like
denominators.
Step 3: Add the fractions. Then add
the whole numbers. Write the answer
in simplest form.
Explain how you know whether your
answer is reasonable.
What other common denominator
could you have used?
7.8 ADD & SUBTRACT MIXED NUMBERS

36. Step 1: Estimate the difference.
Step 2: Find a common denominator.
Use the common denominator to
write equivalent fractions with like
denominators.
Step 3: Subtract the fractions.
Subtract the whole numbers. Write
the answer in simplest form.
Explain how you know whether your
answer is reasonable.
SUBTRACTING MIXED NUMBERS

37. Use the table to solve 25 – 28.
PROBLEM SOLVING PG. 320

38. Use the table to solve.
 Gavin needs to make 2
batches of purple paint.
Explain how you could
find the total amount of
paint Gavin mixed.
7.8 MATH JOURNAL QUESTION

39. ONE WAY – RENAME THE FIRST MIXED EXPLAIN WHY IT IS IMPORTANT TO WRITE
NUMBER EQUIVALENT FRACTIONS BEFORE RENAMING.
 Step 1: Estimate the difference.
 Step 2: Write equivalent fractions,
using the LCD.
 Step 3: Rename 2 3/6 as a mixed
number with a fraction greater than
1.
 Step 4: Find the difference of the
fractions. Then find the difference
of the whole numbers. Write the
answer in simplest form. Check to
make sure your answer is
reasonable.
7.9 SUBTRACTION WITH RENAMING

40. ANOTHER WAY – RENAME BOTH MIXED
NUMBERS AS FRACTIONS GREATER THAN 1.
 Step 1: Write equivalent
fractions, using the LCD.
 Step 2: Rename both mixed
numbers as fractions greater
than 1.
 Step 3: Find the difference of
the fractions. Then write the
answer in simplest form.
SUBTRACTION WITH RENAMING

41. ON YOUR OWN PG. 323

42. CONNECT TO READING PG. 324

43. 7.9 MATH JOURNAL QUESTION
How can you rename to find
the difference of two mixed
numbers?

44. Remember () tell you which operation
to do first.
Unlock the Problem
7.10 USE PROPERTIES OF ADDITION

45. EXAMPLE PG. 326

46. TRY THIS! PG. 326

47. Use the map to solve 10 – 12. 10. In the morning, Julie rides her bike from
the sports complex to the school. In the
afternoon, she rides from the school to the
mall and then to Kyle’s house. How far
does Julie ride her bike?
11. Saturday afternoon, Mario walks from his
house to the library. That evening, Mario
walks from the library to the mall and then
to Kyle’s house. Describe how you use the
properties to find how far Mario walks.
12. Pose a Problem Write and solve a new
problem that uses the distance between
three locations.
PROBLEM SOLVING PG. 328

48. 7.10 MATH JOURNAL QUESTION
How can properties help you add
fractions with unlike
denominators?

49. CHAPTER 7 REVIEW

50. CHAPTER REVIEW