Solve: 2/5 + 1/2 - 1/3 Fraction Addition and Subtraction

Fraction Operations with Mixed Addition and Subtraction

Solve the following exercise:

25+1213=? \frac{2}{5}+\frac{1}{2}-\frac{1}{3}=\text{?}

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Solution
00:03 We want to find the least common denominator
00:06 Therefore we'll multiply by 6, 15, and 10 respectively for the common denominator 30
00:10 Remember to multiply both numerator and denominator
00:30 Let's calculate the multiplications
00:39 Add under common denominator
00:46 Calculate the numerator, one operation at a time
00:55 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

Solve the following exercise:

25+1213=? \frac{2}{5}+\frac{1}{2}-\frac{1}{3}=\text{?}

2

Step-by-step solution

To solve the problem 25+1213\frac{2}{5} + \frac{1}{2} - \frac{1}{3}, we will follow these steps:

  • Step 1: Find the least common denominator (LCD) for 25\frac{2}{5}, 12\frac{1}{2}, and 13\frac{1}{3}.
  • Step 2: Convert each fraction to have this common denominator.
  • Step 3: Perform the arithmetic operations.
  • Step 4: Simplify the result if necessary.

Now, let's proceed with the solution:
Step 1: The denominators are 5, 2, and 3. The least common multiple of these numbers is 30. Thus, the LCD is 30.

Step 2: Convert each fraction to have the common denominator of 30:
- Convert 25\frac{2}{5} to a fraction with denominator 30: 25=2×65×6=1230\frac{2}{5} = \frac{2 \times 6}{5 \times 6} = \frac{12}{30}.
- Convert 12\frac{1}{2} to a fraction with denominator 30: 12=1×152×15=1530\frac{1}{2} = \frac{1 \times 15}{2 \times 15} = \frac{15}{30}.
- Convert 13\frac{1}{3} to a fraction with denominator 30: 13=1×103×10=1030\frac{1}{3} = \frac{1 \times 10}{3 \times 10} = \frac{10}{30}.

Step 3: With all fractions having the same denominator, perform the operations:
1230+15301030=12+151030=1730\frac{12}{30} + \frac{15}{30} - \frac{10}{30} = \frac{12 + 15 - 10}{30} = \frac{17}{30}.

Step 4: Since 1730\frac{17}{30} is in its simplest form, no further simplification is needed.

Therefore, the correct answer is 1730\frac{17}{30}.

3

Final Answer

1730 \frac{17}{30}

Key Points to Remember

Essential concepts to master this topic
  • LCD Rule: Find least common denominator before adding or subtracting fractions
  • Technique: Convert 25 \frac{2}{5} to 1230 \frac{12}{30} when LCD is 30
  • Check: Verify 1230+15301030=1730 \frac{12}{30} + \frac{15}{30} - \frac{10}{30} = \frac{17}{30}

Common Mistakes

Avoid these frequent errors
  • Adding denominators instead of finding LCD
    Don't add 2/5 + 1/2 - 1/3 by doing (2+1-1)/(5+2+3) = 2/10! This completely ignores fraction rules and gives wrong answers. Always find the LCD first, then convert each fraction to equivalent fractions with that common denominator.

Practice Quiz

Test your knowledge with interactive questions

Complete the following exercise:

\( \frac{3}{4}:\frac{5}{6}=\text{?} \)

FAQ

Everything you need to know about this question

Why can't I just add the numerators and denominators separately?

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Because fractions represent parts of different-sized wholes! 12 \frac{1}{2} means 1 out of 2 equal parts, while 13 \frac{1}{3} means 1 out of 3 equal parts. You need the same-sized parts (common denominator) to add them.

How do I find the LCD of 5, 2, and 3?

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List the multiples of each number until you find the smallest one they all share:

  • Multiples of 5: 5, 10, 15, 20, 25, 30...
  • Multiples of 2: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30...
  • Multiples of 3: 3, 6, 9, 12, 15, 18, 21, 24, 27, 30...

The LCD is 30!

What if my final answer is an improper fraction?

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That's okay! 1730 \frac{17}{30} is a proper fraction since 17 < 30. If you get an improper fraction like 3530 \frac{35}{30} , you can convert it to a mixed number: 1530=116 1\frac{5}{30} = 1\frac{1}{6} .

Do I need to simplify 17/30?

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Check if 17 and 30 share any common factors besides 1. Since 17 is prime and doesn't divide into 30, 1730 \frac{17}{30} is already in simplest form!

What's the difference between addition and subtraction with fractions?

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The process is exactly the same! Find the LCD, convert all fractions, then add or subtract the numerators as indicated. Just be careful with your positive and negative signs: +15301030 +\frac{15}{30} - \frac{10}{30} .

Can I use a calculator for this?

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While calculators can help with decimal conversion, it's important to understand the fraction process. Practice doing it by hand first, then use technology to check your work!

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