Addition Subtraction Copyright 1999 Lynda Greene Lesson Finding

Addition & Subtraction Copyright © 1999 Lynda Greene

Lesson – Finding the Least Common Multiple (LCM) Steps: 1. Write out the multiples of the first number. 2. Write out the multiples of the second number. 3. Find the smallest multiple that both numbers have in common. Example: 4: 4, 8, 12, 16, 20, 24 2: 2, 4, 6, 8, 10, 12, 14, 16 5: 5, 10, 15, 20 8: 8 Click Here to Return to Menu

Lesson - Adding Fractions with Unlike Denominators Step: 1. Determine the denominators 2. Find the least common multiple (LCM). 3. Your least common multiple will become your least common denominator (LCD). 4. Generate Equivalent Fractions using the LCM as the LCD. 5. Add or Subtract Fractions. Example: 1. LCM: 3: 2, 4, 6, 8, 10, 12 4: 4, 8, 12 NEXT Click Here

Lesson - Subtracting Fractions with Unlike Denominators Step: 1. Determine the denominators 2. Find the least common multiple (LCM). 3. Your least common multiple will become your least common denominator (LCD). 4. Generate Equivalent Fractions using the LCM as the LCD. 5. Add or Subtract Fractions. Example: 1. LCM: 2: 2, 4, 6 4: 4 Click Here to Return to Menu

Adding & Subtracting Fractions The ‘Butterfly’ Method Copyright © 1999 Lynda Greene

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The “Butterfly” is a short-cut method used for adding & subtracting any two fractions. The usual method is called finding a “Common Denominator” Copyright © 1999 Lynda Greene

Fractions: The Butterfly Method 2 x 5 4 x 3 + Step 1: Draw the wings Copyright © 1999 Lynda Greene

Fractions: The Butterfly Method + 3 x 5 = 15 Step 2: Multiply the denominators Copyright © 1999 Lynda Greene

Fractions: The Butterfly Method 2 x 5 + + 4 x 3 10 + 12 = 22 3 x 5 = 15 Step 3: Compute the new numerators using the Sign in the middle of the 2 fractions. Copyright © 1999 Lynda Greene

Fractions: The Butterfly Method 2 x 5 + + 4 x 3 22 15 Step 4: Simplify the new fraction (answer). Copyright © 1999 Lynda Greene

Practice Problems 1. 2. 3. Copyright © 1999 Lynda Greene

Try These A D B E C F

Try These 17 27 D 10 9 B 13 12 E 41 28 C 19 20 F 26 21 A