G4M5L28 Subtract Mixed Numbers

Module 5
Lesson 28

I can subtract a fraction from a mixed number.

Math Response

Change to an improper fraction

$$3\ \frac{5}{6}$$

Type answer here

Correct Answer: \frac{23}{6}

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Math Response

Change this mixed number to an improper fraction.

$$2\ \frac{1}{4}$$

Type answer here

Correct Answer: \frac{9}{4}

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Math Response

Change $$1\ \frac{4}{5}$$ to an improper fraction

Type answer here

Correct Answer: \frac{9}{5}

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Meredith had 2 m 65 cm of ribbon. She used 87 cm of the ribbon. How
much ribbon did she have left?

Multiple Select

Meredith had 2 m 65 cm of ribbon.

She used 87 cm of the ribbon.

How much ribbon did she have left?

Select all the correct answers.

• 172 cm

• 178 cm

• 352 cm

• 1m 78cm

Meredith had 2
m 65 cm of
ribbon. She
used 87 cm of
the ribbon.
How much
ribbon did she
have left?

Do we have enough fifths to subtract 3 fifths?

3 oranges 2 apples – 1 apple is…?

Materials: (S) Personal white board

Solve the problem.

Problem 1: Subtract a fraction from a mixed number by counting back.

3 dogs 2 puppies – 1 puppy is…?

3 ones 2 fifths – 1 fifth is…?

Math Response

$$3\ \frac{4}{5}\ -\ \frac{1}{5}\ =$$

Type answer here

Correct Answer: 3\frac{3}{5}

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Math Response

$$3\ \frac{4}{5}-\frac{3}{5}\ =$$

Type answer here

Correct Answer: 3\frac{1}{5}

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Now do we have enough fifths?

Do we have enough fifths to subtract 3 fifths?

Problem 2: Subtract a fraction less than 1 from a whole number by
decomposing the subtrahend.

Count back 1 fifth on the number line.

That’s 4.

Model on a number line, and then model using arrows.

Math Response

$$3\ \frac{7}{10}\ -\ \frac{9}{10}\ =$$

Type answer here

Correct Answer: 2\frac{8}{10}

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Math Response

$$4\ \frac{5}{10}\ -\ \frac{7}{10}$$

Type answer here

Correct Answer: 3\frac{8}{10}

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Math Response

$$2\ \frac{1}{4}\ -\ \frac{3}{4}\ =$$

Type answer here

Correct Answer: 1\frac{2}{4}

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Lesson Objective:

Subtract a fraction from a mixed number.

•Use Problems 2(a) and 3(c) to compare the different methods to subtract
when there are not enough fractional units.

•How is 7 tens 3 ones – 9 ones like 7 ones 3 tenths – 9 tenths? How is it
different?

•Tell your partner the process of subtracting a fraction from a mixed number
when regrouping is necessary.

Math Response

$$8\ \frac{3}{8}\ -\ \frac{6}{8}\ =$$

Exit Ticket

Type answer here

Correct Answer: 7\frac{5}{8}

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Math Response

Exit Ticket

$$5\ \frac{5}{6}\ -\frac{4}{6}\ =$$

Type answer here

Correct Answer: 5\frac{1}{6}

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