Solve: 9 × 3⅘ Mixed Number Multiplication Problem

Mixed Number Multiplication with Distributive Property

Solve the following problem:

9×389= 9\times3\frac{8}{9}=

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:05 Let's solve this problem together.
00:08 We'll use the distributive law to make it easier.
00:12 Break down three and eight ninths into four minus one ninth.
00:18 Multiply the number outside by each part inside the brackets.
00:22 Find each product separately, then subtract.
00:26 Let's simplify everything we can.
00:29 And that's how we find the solution!

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Solve the following problem:

9×389= 9\times3\frac{8}{9}=

2

Step-by-step solution

Apply the distributive property of multiplication in order to break down the fraction into a subtraction exercise between a whole number and a fraction. This allows us to work with smaller numbers and simplify the operation

Reminder - The distributive property of multiplication allows us to break down the larger term in a multiplication problem into a sum or difference of smaller numbers, which makes multiplication easier and gives us the ability to solve the problem without using a calculator

9×(419)= 9\times(4-\frac{1}{9})=

Apply the distributive property formula a(b+c)=ab+ac a(b+c)=ab+ac

(9×4)(9×19)= (9\times4)-(9\times\frac{1}{9})=

Proceed to solve what's inside of the left parentheses:

9×4=36 9\times4=36

Note that in the right parentheses we can reduce 9 by 9 as follows:

9=91 9=\frac{9}{1}

91×19=9×11×9=99=11=1 \frac{9}{1}\times\frac{1}{9}=\frac{9\times1}{1\times9}=\frac{9}{9}=\frac{1}{1}=1

We obtain the following exercise:

361=35 36-1=35

Shown below are the various steps of the solution:

9×389=9×(419)=(9×4)(9×19)=361=35 9\times3\frac{8}{9}=9\times(4-\frac{1}{9})=(9\times4)-(9\times\frac{1}{9})=36-1=35

3

Final Answer

35 35

Key Points to Remember

Essential concepts to master this topic
  • Rule: Convert mixed numbers using 389=419 3\frac{8}{9} = 4 - \frac{1}{9}
  • Technique: Apply distributive property: 9×(419)=361 9 \times (4 - \frac{1}{9}) = 36 - 1
  • Check: Substitute back: 9×389=9×359=35 9 \times 3\frac{8}{9} = 9 \times \frac{35}{9} = 35

Common Mistakes

Avoid these frequent errors
  • Converting mixed number incorrectly to improper fraction
    Don't just multiply whole number by denominator and add numerator = 359 \frac{35}{9} which gives 358081 35\frac{80}{81} ! This creates unnecessarily complex calculations. Always use the distributive property by rewriting 389 3\frac{8}{9} as 419 4 - \frac{1}{9} for simpler arithmetic.

Practice Quiz

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\( 100-(30-21)= \)

FAQ

Everything you need to know about this question

Why rewrite 389 3\frac{8}{9} as 419 4 - \frac{1}{9} instead of 359 \frac{35}{9} ?

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The distributive property method makes calculations much easier! Instead of multiplying 9×359 9 \times \frac{35}{9} , you get simple operations: 9×4=36 9 \times 4 = 36 and 9×19=1 9 \times \frac{1}{9} = 1 .

How do I know when to use the distributive property?

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Use it when the fractional part is close to 1, like 89 \frac{8}{9} . Since 89=119 \frac{8}{9} = 1 - \frac{1}{9} , you can rewrite the mixed number as one less whole number plus the complement fraction.

What if I get confused with the subtraction?

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Remember: 389=3+89=3+(119)=419 3\frac{8}{9} = 3 + \frac{8}{9} = 3 + (1 - \frac{1}{9}) = 4 - \frac{1}{9} . Think of it as borrowing 1 from the next whole number!

Can I always use this method for mixed number multiplication?

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This works best when the fraction is close to 1 (like 78 \frac{7}{8} , 89 \frac{8}{9} , 910 \frac{9}{10} ). For other fractions, converting to improper fractions might be easier.

How do I check my answer is correct?

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Convert your mixed number to an improper fraction and multiply: 389=359 3\frac{8}{9} = \frac{35}{9} , so 9×359=35 9 \times \frac{35}{9} = 35 . Both methods should give the same answer!

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