Solve: Adding Fractions 3/5 + 1/3 + 2/15 Step by Step

Fraction Addition with Multiple Denominators

35+13+215= \frac{3}{5}+\frac{1}{3}+\frac{2}{15}=

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Solve
00:03 We want to find the least common denominator
00:06 Therefore we'll multiply by 3 and 5 respectively to find the common denominator
00:09 Remember to multiply both numerator and denominator
00:22 Let's calculate the multiplications
00:32 Let's add under the common denominator
00:38 Let's calculate the numerator
00:45 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

35+13+215= \frac{3}{5}+\frac{1}{3}+\frac{2}{15}=

2

Step-by-step solution

To solve this problem, we'll follow these steps:

  • Step 1: Find the least common multiple (LCM) of the denominators: 5, 3, and 15.
  • Step 2: Convert each fraction to an equivalent fraction with the LCM as the common denominator.
  • Step 3: Add the numerators of the converted fractions.
  • Step 4: Simplify the resulting fraction if necessary.

Now, let's work through each step:

Step 1: The denominators are 5, 3, and 15. The LCM of these numbers is 15.

Step 2: Convert each fraction:

  • 35=3×35×3=915 \frac{3}{5} = \frac{3 \times 3}{5 \times 3} = \frac{9}{15}
  • 13=1×53×5=515 \frac{1}{3} = \frac{1 \times 5}{3 \times 5} = \frac{5}{15}
  • 215=215 \frac{2}{15} = \frac{2}{15}

Step 3: Add the numerators of the converted fractions:

915+515+215=9+5+215=1615 \frac{9}{15} + \frac{5}{15} + \frac{2}{15} = \frac{9 + 5 + 2}{15} = \frac{16}{15}

Step 4: The fraction 1615 \frac{16}{15} is already in simplest form.

Therefore, the solution to the problem is 1615 \frac{16}{15} .

3

Final Answer

1615 \frac{16}{15}

Key Points to Remember

Essential concepts to master this topic
  • LCM Rule: Find least common multiple of all denominators first
  • Technique: Convert 35 \frac{3}{5} to 915 \frac{9}{15} by multiplying by 3
  • Check: Verify 915+515+215=1615 \frac{9}{15} + \frac{5}{15} + \frac{2}{15} = \frac{16}{15}

Common Mistakes

Avoid these frequent errors
  • Adding numerators and denominators separately
    Don't add 3+1+2 = 6 and 5+3+15 = 23 to get 623 \frac{6}{23} ! This ignores the need for common denominators and gives completely wrong results. Always find the LCM first and convert all fractions before adding numerators.

Practice Quiz

Test your knowledge with interactive questions

\( \)\( \frac{4}{5}+\frac{1}{5}= \)

FAQ

Everything you need to know about this question

Why is the LCM of 5, 3, and 15 equal to 15?

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The LCM is the smallest number that all denominators divide into evenly. Since 15 ÷ 5 = 3, 15 ÷ 3 = 5, and 15 ÷ 15 = 1, the number 15 works perfectly!

What if the fractions don't have a nice LCM like 15?

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Sometimes you'll need to find larger LCMs. For example, with denominators 4, 6, and 9, the LCM would be 36. The process stays the same - just convert each fraction using the LCM.

Do I always need to simplify my final answer?

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Yes, if possible! However, 1615 \frac{16}{15} is already in simplest form because 16 and 15 share no common factors other than 1.

Can I convert to decimals instead of finding the LCM?

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You could, but you might get messy decimals that are hard to work with. The LCM method keeps everything as exact fractions, which is usually cleaner and more accurate.

What if one denominator is already the LCM?

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Great! Like 215 \frac{2}{15} in this problem - it stays exactly the same. You only need to convert the other fractions to match this denominator.

How do I know which number to multiply by when converting?

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Divide the LCM by the original denominator. For 35 \frac{3}{5} : 15 ÷ 5 = 3, so multiply both numerator and denominator by 3 to get 915 \frac{9}{15} .

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