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PPT – Learn to add and subtract fractions with unlike denominators. PowerPoint presentation | free to download - id: 6ce430-NjQ3N

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Learn to add and subtract fractions with unlike

denominators.

Vocabulary

least common denominator (LCD)?

The Pacific Ocean covers of Earths surface.

The Atlantic Ocean covers of Earths

surface. To find the fraction of Earths surface

that is covered by both oceans, you can add

and , which are unlike fractions.

To add or subtract unlike fractions, first

rewrite them as equivalent fractions with a

common denominator.

Remember!

Fractions that represent the same value are

equivalent.

Additional Example 1 Cooking Application Mark

made a pizza with pepperoni covering of

the pizza and onions covering another . What

fraction of the pizza is covered by pepperoni and

onions?

Find a common denominator for 4 and 3 4 x 3

12.

_____

Additional Example 1 Continued

Write equivalent fractions with 12 as the common

denominator.

Add the numerators. Keep the common denominator.

_______

_____

The pepperoni and onions cover of the pizza.

Check It Out Example 1 Tori made a pizza with

peppers covering of the pizza and ham

covering another . What fraction of the pizza

is covered by ham and peppers?

?

Find a common denominator for 3 and 2 3 X 2 6.

_____

Check It Out Example 1 Continued

Write equivalent fractions with 6 as the common

denominator.

Add the numerators. Keep the common denominator.

_______

_____

You can use any common denominator or the least

common denominator to add and subtract unlike

fractions. The least common denominator (LCD) is

the least common multiple of the denominators.

Additional Example 2A Adding and Subtracting

Unlike Fractions Add or subtract. Write each

answer in simplest form. Method 1 Multiplying

denominators.

Multiply the denominators. 10 8 80

Write equivalent fractions with a common

denominator.

Subtract.

Write the answer in simplest form.

Additional Example 2B Adding and Subtracting

Unlike Fractions Add or subtract. Write each

answer in simplest form. Method 2 Use the LCD.

Multiples of 12 12, 24,

Multiples of 8 8, 16, 24, The LCD is 24.

Write equivalent fractions with a common

denominator.

Subtract.

Additional Example 2C Adding and Subtracting

Unlike Fractions Add or subtract. Write each

answer in simplest form. Method 3 Use mental

math.

Think 16 is a multiple of 8, so the LCD is 16.

Rewrite with a denominator of 16.

Add.

Additional Example 2D Adding and Subtracting

Unlike Fractions Add or subtract. Write each

answer in simplest form. Method 3 Use mental

math.

Think 16 is a multiple of 8, so the LCD is 16.

Rewrite with a denominator of 16.

Subtract.

Check It Out Example 2A Add or subtract. Write

each answer in simplest form. Method 1

Multiplying denominators.

Multiply the denominators. 10 6 60

Write equivalent fractions with a common

denominator.

Subtract.

Write the answer in simplest form.

Check It Out Example 2B Add or subtract. Write

each answer in simplest form. Method 2 Use the

LCD.

Multiples of 7 7, 14, 21,

Multiples of 3 3, 6, 9, 12, 15, 18, 21, The

LCD is 21.

Write equivalent fractions.

Subtract.

Check It Out Example 2C Add or subtract. Write

each answer in simplest form. Method 3 Use

mental math.

Think 12 is a multiple of 6, so the LCD is 12.

Rewrite with a denominator of 12.

Add.

Check It Out Example 2D Add or subtract. Write

each answer in simplest form. Method 3 Use

mental math.

Think 12 is a multiple of 6, so the LCD is 12.

Rewrite with a denominator of 12.

Subtract.