Solve Mixed Number Addition: 2⅓ + 1¼ Step by Step

Mixed Number Addition with Unlike Denominators

213+114= 2\frac{1}{3}+1\frac{1}{4}=

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Solve
00:03 First convert mixed fractions to fractions
00:43 Multiply each fraction by the second denominator to find the common denominator
00:53 Calculate the multiplications
01:03 Add with the common denominator
01:11 Now convert to a mixed fraction
01:21 Break down 43 into 36 plus 7
01:28 Break down the fraction into whole number and remainder
01:33 Convert from whole fraction to whole number, and combine with mixed fraction
01:42 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

213+114= 2\frac{1}{3}+1\frac{1}{4}=

2

Step-by-step solution

To solve the addition of the mixed numbers 213+114 2\frac{1}{3} + 1\frac{1}{4} , we'll go through the following steps:

  • Step 1: Convert the mixed numbers to improper fractions.
  • Step 2: Find a common denominator for the fractions.
  • Step 3: Add the fractions together.
  • Step 4: Convert, if necessary, back to a mixed number for the final answer.

Let's go through each step in detail:

Step 1: Convert each mixed number to an improper fraction.

For 213 2\frac{1}{3} :
Convert by using the formula abc=ac+bc a\frac{b}{c} = \frac{ac + b}{c} .
This gives us 213=23+13=73 2\frac{1}{3} = \frac{2 \cdot 3 + 1}{3} = \frac{7}{3} .

For 114 1\frac{1}{4} :
Similarly, 114=14+14=54 1\frac{1}{4} = \frac{1 \cdot 4 + 1}{4} = \frac{5}{4} .

Step 2: Find a common denominator.

The denominators are 3 and 4, so the least common denominator (LCD) is 12.
Convert 73 \frac{7}{3} to an equivalent fraction with denominator 12:
73=7434=2812 \frac{7}{3} = \frac{7 \cdot 4}{3 \cdot 4} = \frac{28}{12} .

Convert 54 \frac{5}{4} to an equivalent fraction with denominator 12:
54=5343=1512 \frac{5}{4} = \frac{5 \cdot 3}{4 \cdot 3} = \frac{15}{12} .

Step 3: Add the fractions together.
2812+1512=28+1512=4312 \frac{28}{12} + \frac{15}{12} = \frac{28 + 15}{12} = \frac{43}{12} .

Step 4: Convert back to a mixed number if necessary.

The improper fraction 4312\frac{43}{12} can be converted back to a mixed number.
Perform the division 43÷12 43 \div 12 to get the quotient as 3 and a remainder of 7.
Thus, 4312=3712 \frac{43}{12} = 3\frac{7}{12} .

Therefore, the solution to the problem is 3712 3\frac{7}{12} .

3

Final Answer

3712 3\frac{7}{12}

Key Points to Remember

Essential concepts to master this topic
  • Rule: Convert mixed numbers to improper fractions first
  • Technique: Find LCD: denominators 3 and 4 give LCD = 12
  • Check: Convert answer back to mixed number: 4312=3712 \frac{43}{12} = 3\frac{7}{12}

Common Mistakes

Avoid these frequent errors
  • Adding whole numbers and fractions separately without finding common denominator
    Don't add 2 + 1 = 3, then try to add 13+14 \frac{1}{3} + \frac{1}{4} without LCD = wrong result like 327 3\frac{2}{7} ! This ignores that fractions need common denominators. Always convert to improper fractions first, then find the LCD for proper addition.

Practice Quiz

Test your knowledge with interactive questions

\( 5:\frac{2}{5}= \)

FAQ

Everything you need to know about this question

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

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You can add whole numbers separately, but you still need a common denominator for the fractions! For 13+14 \frac{1}{3} + \frac{1}{4} , you need LCD = 12 to get 412+312=712 \frac{4}{12} + \frac{3}{12} = \frac{7}{12} .

How do I find the LCD of 3 and 4?

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List multiples of each number: 3: 3, 6, 9, 12... and 4: 4, 8, 12... The first number that appears in both lists is 12, so LCD = 12.

What's the formula for converting mixed numbers to improper fractions?

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Use abc=ac+bc a\frac{b}{c} = \frac{ac + b}{c} . For example: 213=2×3+13=73 2\frac{1}{3} = \frac{2 \times 3 + 1}{3} = \frac{7}{3} . Multiply whole number by denominator, add numerator!

How do I convert an improper fraction back to a mixed number?

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Divide the numerator by denominator. For 4312 \frac{43}{12} : 43 ÷ 12 = 3 remainder 7, so the answer is 3712 3\frac{7}{12} .

Do I always need to simplify my final answer?

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Yes! Always check if your fraction can be simplified. In this case, 712 \frac{7}{12} is already in lowest terms since 7 and 12 share no common factors.

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