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Multiplying Mixed Numbers: Word Problems

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Multiplying Mixed Numbers – Word Problems

Understanding how to work with mixed numbers is essential in our daily lives. From cooking recipes to measuring materials for a project, we often encounter situations where mixed numbers come into play. Gaining comfort in multiplying these numbers helps in effectively solving real-world problems.

Mixed Numbers and Improper Fractions

It's really helpful to know about improper fractions and mixed numbers when you're solving maths problems, so let's make sure we understand what they are!

Mixed Number: A number consisting of a whole number and a fraction, like 2½.

Improper Fraction: A fraction where the numerator (top number) is greater than or equal to the denominator (bottom number), such as $\frac{7}{4}$.

27595_MultiplyingMixedNumbers-01.svg

Conversion between Mixed Numbers and Improper Fractions

Process Description Example
Mixed to Improper Conversion Multiply the whole number by the denominator, add the numerator, then place over the denominator. $2 \frac{1}{2}$ → $\frac{2 \times 2 + 1}{2}$ = $\frac{5}{2}$
Improper to Mixed Conversion Divide the numerator by the denominator. The quotient is the whole number, the remainder over the denominator is the fraction. $\frac{7}{4}$ → $1 \frac{3}{4}$

Convert the mixed number $3 \frac{1}{4}$ to an improper fraction.

  • Multiply the whole number part by the denominator and add the numerator.
  • $3 \times 4 + 1 = 12 + 1 = 13$.
  • The mixed number $3 \frac{1}{4}$ is equal to the improper fraction $\frac{13}{4}$.

Convert the improper fraction $\frac{11}{3}$ to a mixed number.

  • Divide the numerator by the denominator.
  • $11 \div 3 = 3$ remainder $2$.
  • The improper fraction $\frac{11}{3}$ is equal to the mixed number $3 \frac{2}{3}$.

Multiplying Mixed Numbers: Word Problems – Step-by-Step Process

Multiplying a fraction by a whole number and dealing with two mixed numbers are common in real-world problems. It's important to understand how these calculations work in practical situations. Let’s practise some examples!

27595_MultiplyingMixedNumbers-02.svg

A recipe needs $1 \frac{2}{3}$ cups of sugar for a batch of cookies, and you want to make $2 \frac{1}{2}$ batches.

  • Convert Mixed to Improper: Convert $1 \frac{2}{3}$ to $\frac{5}{3}$ and $2 \frac{1}{2}$ to $\frac{5}{2}$.
  • Multiply: Multiply $\frac{5}{3}$ by $\frac{5}{2}$.
  • Calculate & Convert Back: $\frac{5}{3} \times \frac{5}{2} = \frac{25}{6}$. Convert $\frac{25}{6}$ to a mixed number: $4 \frac{1}{6}$. You need $4 \frac{1}{6}$ cups of sugar.

If a garden requires $2 \frac{1}{4}$ cubic metres of soil for each section, and you are landscaping $3$ sections, how much soil is needed in total?

27595_MultiplyingMixedNumbers-03.svg

  • Convert Mixed to Improper: Convert $2 \frac{1}{4}$ to an improper fraction: $\frac{2 \times 4 + 1}{4} = \frac{9}{4}$.
  • Multiply: Multiply by 3: $\frac{9}{4} \times 3$.
  • Calculate & Convert Back: $\frac{27}{4} = 6 \frac{3}{4}$. You need $6 \frac{3}{4}$ cubic metres of soil.

Each shelf needs $2 \frac{1}{2}$ feet of wood, and you are building $4$ shelves. How much wood in total?

27595_MultiplyingMixedNumbers-04.svg

  • Convert Mixed to Improper: Convert $2 \frac{1}{2}$ to $\frac{5}{2}$.
  • Multiply: Multiply by 4: $\frac{5}{2} \times 4$.
  • Calculate & Convert Back: $\frac{20}{2} = 10$. You need $10$ feet of wood.

Multiplying Mixed Numbers: Word Problems – Practice

Practise some on your own!

Multiplying Mixed Numbers: Word Problems – Summary

Key Learnings from this Text:

  • Multiplying mixed numbers is a practical skill for real-world applications.
  • Conversion between mixed and improper fractions is key in multiplying mixed numbers.
  • Multiplying mixed numbers involves converting to improper fractions, multiplying, and converting back.
  • Understanding these steps helps in efficiently solving problems involving measurements, recipes, etc.

Multiplying Mixed Numbers: Word Problems – Frequently Asked Questions

Multiplying Mixed Numbers: Word Problems exercise

Would you like to apply the knowledge you’ve learnt? You can review and practice it with the tasks for the learning text Multiplying Mixed Numbers: Word Problems.
  • Hints

    Convert the mixed number $3 \frac{3}{4}$​​​ into an improper fraction by multiplying the whole number by the denominator of the fraction part and then adding the numerator.

    Multiply the resulting improper fraction by the number of sections to find the total amount of wood needed.

    Solution

    1.) First, we convert $3 \frac{3}{4}$​​ to an improper fraction.

    2.) Convert $3 \frac{3}{4}$​​ to an improper fraction:

    $3 \times 4 + 3 = 15 \rightarrow \frac{15}{4}$​

    3.) Multiply the improper fraction by the number of sections:

    $\frac{15}{4}​ \times 4 = \frac{60}{4}​ = 15$

    4.) We now have the correct answer of $15$ metres.

  • Hints

    Convert $2 \frac{1}{2}$​ to an improper fraction:

    $2 \times 2 + 1 = 5 \rightarrow \frac{5}{2}$​

    Multiply the improper fraction by the number of guests:

    $\frac{5}{2}​ \times 5 = \frac{25}{2}$​

    Convert $\frac{25}{2}$​​ back to a mixed number.

    Solution

    They eat $12 \frac{1}{2}$ slices of pizza.

  • Hints

    Convert the mixed number $1 \frac{3}{5}$​ into an improper fraction by multiplying the whole number part by the denominator of the fractional part and then adding the numerator.

    Multiply the resulting improper fraction by the number of students to find out the total number of tubes needed for the class, and then convert the answer to a mixed number if necessary.

    Solution

    $12\mathbf{\frac{4}{5}}$ tubes of paint are used by all the students.

    1. Convert $1 \frac{3}{5}$ to an improper fraction: $1 \times 5 + 3 = 8 \rightarrow \frac{8}{5}$

    2. $\frac{8}{5} \times 8 = \frac{64}{5} = 12 \frac{4}{5}$

  • Hints

    Convert both mixed numbers into improper fractions.

    Multiply the numerators and multiply the denominators.

    Convert this answer back to a mixed number.

    Solution

    Sandy will use $7\frac{1}{2}$ packets of seeds.

    Convert $3\frac{1}{3}$ to an improper fraction - $\frac{10}{3}$

    Convert $2\frac{1}{4}$ to an improper fraction - $\frac{9}{4}$

    Multiply $\frac{10}{3} \times \frac{9}{4} = \frac{90}{12}$

    Convert $\frac{90}{12}$ to a mixed number - $7\frac{6}{12}$ which is simplified to $7\frac{1}{2}$.

  • Hints

    Convert $1 \frac{1}{3}$ to an improper fraction by multiplying $1 \times 3$ and adding $1$.

    When multiplying the improper fraction by a whole number, multiply the numerator only.

    Solution

    The total amount of sugar needed to make 3 batches of cookies is 4 cups.

    1.) $1 \frac{1}{3}$ = $\frac{4}{3}$

    2.) $\frac{4}{3} \times 3 =$ $\frac{12}{3}$

    3.) $\frac{12}{3}$ = $4$

    4.) The total amount of sugar needed to make $3$ batches of cookies is $4$ cups.

  • Hints

    Convert the mixed numbers to improper fractions before multiplying.

    When multiplying a fraction by a single number, just multiply the numerator.

    When multiplying two fractions, multiply the numerators and multiply the denominators.

    Solution

    $3\frac{1}{10} \times 3 = 9\frac{3}{10}$

    $4\frac{1}{2} \times 2\frac{1}{6} = 9\frac{3}{4}$

    $5\frac{2}{3} \times 2 = 11\frac{1}{3}$

    $1\frac{3}{4} \times 3\frac{1}{4} = 5\frac{11}{16}$

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