Addition & Subtractionof Rational Numbers

(Fractions)a Strategic Intervention Material

by: JAY AHR EBUEN SISONBancal Integrated School

Division of ZambalesRegion III

How to use this material?

ANSWER CARD

ENRICHMENT CARDASSESSMENT CARDS

ACTIVITY #4Addition/Subtraction of

Dissimilar Fraction ACTIVITY #3Least Common Multiple ACTIVITY #2

Addition/Subtraction of Similar Fraction

ACTIVITY #1SIMILAR or DISSIMILAR

OVERVIEWGUIDE CARD

Hey guys, Let’s start with this one.

GUIDE CARDLEARNING COMPETENCYLeast Mastered Skill

Addition and subtraction of similar and dissimilar fractionsSub-Tasks:

1. Define and identify similar fractions and dissimilar fractions

2. Perform addition and subtraction of similar fraction

3. Determine Least Common Denominator (LCD) between Dissimilar Fractions

4. Evaluate rational expressions involving addition and subtraction

3/4 + 1/3 = 1 1/12 how we do we compute it mathematically?

Let’s take a look at this…+ = = =

ACTIVITY #1Similar or

Dissimilar ?Similar fractions are fractions that have same or common

denominator. They are often called like fractions. If they are NOT same or common, then they are dissimilar fractions.

Let’s try to identify the following pairs of fractions as similar or dissimilar. WriteS if they are similar fractions or D if they are dissimilar fractions in the space providedfor each number.

___ 1. and ___ 2. and 2 ___ 3. and 3 ___ 4. and ___ 5. 3 and

These seem so easy, right?

ACTIVITY #2Addition and Subtraction of

Similar FractionsIn addition or subtraction of similar fractions, we only add

or subtract their numerator and rewrite the same or common denominator.

Example #1: find the sum of +

+ 1

Example #2: Find the difference of - -

Answers should always express in simplified form.

ACTIVITY #2Addition and Subtraction of

Similar FractionsNow, let’s try to perform the indicated operation of the

following similar fractions.

1. +

2. +

3. 1 - 4. - 5. + -

Let’s do this…

ACTIVITY #3Least Common Multiple (LCM) Least common multiple is the smallest multiple that is

exactly divisible by every member of a set of numbers. This is use to make dissimilar fractions be similar by changing them into equivalent fractions having LCM as their common denominator.

Example: Find the least common multiple of 12 and 18.by listing:

multiples of 12: 12 , 24 , 36 , 48 , 60 , 72 , 84 , 96

multiples of 18: 18 , 36 , 54 , 72 , 90 , 108 , 126

since we have two common multiples on the list, 36 & 72,

and the least common multiple between them is 36

by factoring:factors of 12: 2 × 2 × 3

least common multiple can get factors of 18: 2 × × 3 × 3 by

listing down all common & LCM: 2 × 2 × 3 × 3 = 36

uncommon factors and multiply them.

ACTIVITY #3Least Common Multiple (LCM) Let’s try to fine the least common multiple of these given

set of numbers.

1. 4 and 6

2. 6 and 18

3. 12 and 16

4. 24 and 18

5. 4 , 6 and 9

You can find the LCM through listing multiples or by

factoring. You can use any of the said

methods

ACTIVITY #4Addition and Subtraction of

Dissimilar FractionsFind the sum of + Dissimilar fractions, right? The LCM of

the denominators of each fractions is also known as the Least Common Denominator (LCD).

Let’s make these dissimilar fractions into similar fractions. Identify first the LCM.

Using factoring: factors of 12: 2 × 2 × 3

factors of 18: 2 × × 3 × 3

LCM: 2 × 2 × 3 × 3 = 36

then change the given fractions to their equivalents fraction using LCM as their least common denominator (LCD).

=

Now that we have similar fractions, we can proceed to the operation indicated.

+ =

To find the numerator of the equivalent fractions, divide the LCD by the given denominator and multiply the result to the given numerator.

Assessment CardAddition and Subtraction of

Dissimilar FractionsDetermine the least common multiple of each

denominators, and perform the indicated operations.

1. +

2. +

3. - 4. - 5. + -

You can find the LCM through listing multiples or by

factoring. You can use any of the said

methods

Enrichment CardWork ProblemIt takes 3 hours for Tim to mow the lawn. Linda can mow

the same lawn in 5 hours. How long will it take John and Linda, work together, to mow the lawn?

Note: If A can do a piece of work in n time, then A’s rate of work =

Tim’s rate of work () + Linda’s rate of work () = () x = time spend of both

working together

= + = = = x = = 1.825 hours

= multiply both side by 15x therefore, it takes 1 hours 52 minutes

and 30 seconds for John & Linda 15 = 8x divide both side by 8 working

together to mow the lawn.

rate of work when they both working together

Reference Card

Mathematics 7 Learner’s Module, pp.48 – 51

CPM Educational Program 2011http://pdfs.cpm.org/skillBuilders/MC/MC_Addition_Subtraction_of_Fractions.pdf

Spectrum Math Grade 7, pp. 27 - 48

Answer CardActivity #1

Assessment1. S

1. 2. D

2. 3. S

3. 4. D

4. 5. S

5. Activity #2

1. 2. 13. 4. 5.

Activity #31. 122. 183. 484. 725. 36