FRACTIONS Addition & Subtraction of Unlike Fractions

FRACTIONS

Addition & Subtraction of Unlike Fractions

2 3

+

1 5

🔍 Check denominators: 3 and 5 are different
Type: Unlike fractions

❓ What should we do with unlike fractions?
✅ Find the LCM/LCD to make them like fractions!

Find LCM/LCD of 3 and 5:
Multiples of 3: 3, 6, 9, 12, 15, 18...
Multiples of 5: 5, 10, 15, 20...
LCM = 15

Method: Cross Multiplication

2

1

↗↖

3

5

Step 1: (2)(5) + (1)(3) (3)(5)

Step 2: 10 + 3 15

Result: 13 15

4 5

-

2 7

🔍 Check denominators: 5 and 7 are different
Type: Unlike fractions

❓ What should we do with unlike fractions?
✅ Find the LCM/LCD to make them like fractions!

Find LCM/LCD of 5 and 7:
Multiples of 5: 5, 10, 15, 20, 25, 30, 35...
Multiples of 7: 7, 14, 21, 28, 35...
LCM = 35

Method: Cross Multiplication

4

2

↗↖

5

7

Step 1: (4)(7) - (2)(5) (5)(7)

Step 2: 28 - 10 35

Result: 18 35

5 8

+

1 6

🔍 Check denominators: 8 and 6 are different
Type: Unlike fractions

❓ What should we do with unlike fractions?
✅ Find the LCM/LCD to make them like fractions!

Find LCM/LCD of 8 and 6:

Least Common Multiple

2	8, 6
2	4, 3
2	2, 3
3	1, 3
	1, 1

LCM = 2 × 2 × 2 × 3 = 24

Step 1 - Convert to equivalent fractions:
5 8 = 5 × 3 24 = 15 24

1 6 = 1 × 4 24 = 4 24

Step 2 - Add like fractions: 15 + 4 24 = 19 24

Result: 19 24 (Already in simplest form)

8 3

-

2 9

🔍 Check denominators: 3 and 9 are different
Type: Unlike fractions

❓ What should we do with unlike fractions?
✅ Find the LCM/LCD to make them like fractions!

Find LCM/LCD of 3 and 9:

Least Common Multiple

3	3, 9
3	1, 3
	1, 1

LCM = 3 × 3 = 9

Step 1 - Convert to equivalent fractions:
8 3 = 8 × 3 9 = 24 9

2 9 = 2 × 1 9 = 2 9

Step 2 - Subtract like fractions: 24 - 2 9 = 22 9

Result: 22 9 (Already in simplest form)

🎯 Practice Time! 🎯

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Click for tips! Use cross multiplication to solve fractions with different denominators!