Solve Mixed Number Division: 3½ ÷ 1¼ Step-by-Step

Mixed Number Division with Improper Fractions

312:114= 3\frac{1}{2}:1\frac{1}{4}=

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:06 Let's start by solving this problem.
00:09 First, change mixed fractions to simple fractions.
00:31 Next, write the division as a fraction.
00:39 Then, multiply by the reciprocal.
00:48 Now, calculate the products carefully.
00:54 Convert your answer back to a mixed fraction.
00:58 Here, break 28 into 20 plus 8.
01:02 Separate the fraction into a whole number and remainder.
01:07 Combine the proper fraction with the mixed number.
01:16 Simplify everything if possible.
01:28 And that's how we find the solution to the problem!

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

312:114= 3\frac{1}{2}:1\frac{1}{4}=

2

Step-by-step solution

To solve the problem 312:114 3\frac{1}{2} : 1\frac{1}{4} , we will follow these steps:

  • Step 1: Convert each mixed number to an improper fraction.
  • Step 2: Divide the improper fractions by multiplying by the reciprocal of the second fraction.
  • Step 3: Simplify the resulting fraction if possible.
  • Step 4: Convert the simplified improper fraction back to a mixed number if needed.

Let's work through each step:

Step 1: Convert 312 3\frac{1}{2} to an improper fraction.

312=(3×2)+12=6+12=72 3\frac{1}{2} = \frac{(3 \times 2) + 1}{2} = \frac{6 + 1}{2} = \frac{7}{2}

Convert 114 1\frac{1}{4} to an improper fraction.

114=(1×4)+14=4+14=54 1\frac{1}{4} = \frac{(1 \times 4) + 1}{4} = \frac{4 + 1}{4} = \frac{5}{4}

Step 2: Divide 72 \frac{7}{2} by 54 \frac{5}{4} .

The division of fractions is done by multiplying by the reciprocal: 72×45 \frac{7}{2} \times \frac{4}{5} .

Step 3: Perform the multiplication.

7×42×5=2810 \frac{7 \times 4}{2 \times 5} = \frac{28}{10}

Step 4: Simplify 2810 \frac{28}{10} .

Divide both the numerator and the denominator by 2: 28÷210÷2=145 \frac{28 \div 2}{10 \div 2} = \frac{14}{5} .

Convert 145 \frac{14}{5} back to a mixed number.

145=245 \frac{14}{5} = 2\frac{4}{5} because 14 divided by 5 is 2 with a remainder of 4.

Therefore, the solution to the problem 312:114 3\frac{1}{2} : 1\frac{1}{4} is 245 2\frac{4}{5} .

3

Final Answer

245 2\frac{4}{5}

Key Points to Remember

Essential concepts to master this topic
  • Conversion Rule: Transform mixed numbers into improper fractions first
  • Division Technique: Multiply by reciprocal: 72×45=2810 \frac{7}{2} \times \frac{4}{5} = \frac{28}{10}
  • Verification: Convert back to mixed number and check: 145=245 \frac{14}{5} = 2\frac{4}{5}

Common Mistakes

Avoid these frequent errors
  • Dividing mixed numbers directly without conversion
    Don't try to divide 312÷114 3\frac{1}{2} ÷ 1\frac{1}{4} as mixed numbers = confusion and wrong answers! Mixed numbers can't be divided directly using standard algorithms. Always convert to improper fractions first: 72÷54 \frac{7}{2} ÷ \frac{5}{4} , then multiply by the reciprocal.

Practice Quiz

Test your knowledge with interactive questions

\( 1\frac{4}{5}\times1\frac{1}{3}= \)

FAQ

Everything you need to know about this question

Why can't I just divide the whole numbers and fractions separately?

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Because mixed numbers represent one complete value, not separate parts! 312 3\frac{1}{2} means 3.5, not "3 and some fraction." You must convert to improper fractions to preserve the true mathematical value.

How do I remember which fraction to flip when dividing?

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Always flip the second fraction (the divisor). Think: "Keep, Change, Flip" - keep the first fraction, change division to multiplication, flip the second fraction. So 72÷54 \frac{7}{2} ÷ \frac{5}{4} becomes 72×45 \frac{7}{2} \times \frac{4}{5} .

What if my final fraction is bigger than 1?

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That's normal! When dividing mixed numbers, you often get improper fractions. Just convert back to a mixed number: divide the numerator by denominator, and the remainder becomes the new numerator.

Do I always need to simplify my answer?

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Yes, always simplify! Look for common factors in your fraction. In this problem, 2810 \frac{28}{10} simplifies to 145 \frac{14}{5} by dividing both parts by 2.

How can I check if my mixed number conversion is correct?

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Multiply the whole number by the denominator, then add the numerator. For 312 3\frac{1}{2} : (3 × 2) + 1 = 7, so it equals 72 \frac{7}{2} . Always double-check this step!

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