Solve the Fraction Equation: Finding the Missing Addend in 2/8 + ? = 3/5

Fraction Addition with Missing Addends

28+?=35 \frac{2}{8}+?=\frac{3}{5}

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:05 Let's find the unknown value.
00:09 First, rearrange the equation to isolate the unknown.
00:20 To simplify, find the smallest common denominator.
00:25 Multiply each fraction by the second denominator.
00:31 Be sure to multiply both the numerator and denominator.
00:42 Now, calculate the products.
00:52 Let's add them under the common denominator.
00:56 Calculate the sum in the numerator.
01:01 Reduce the fraction as much as you can.
01:07 Remember, divide both the numerator and denominator.
01:14 And that's how we solve the problem!

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

28+?=35 \frac{2}{8}+?=\frac{3}{5}

2

Step-by-step solution

To solve this problem, we'll proceed with the following steps:

  • Step 1: Simplify the fraction 28 \frac{2}{8} .
  • Step 2: Determine a common denominator for 14 \frac{1}{4} and 35 \frac{3}{5} .
  • Step 3: Subtract 14 \frac{1}{4} from 35 \frac{3}{5} with this common denominator.
  • Step 4: Simplify the result if necessary.

Now, let's work through each step:

Step 1: Simplify 28 \frac{2}{8} to 14 \frac{1}{4} since both 2 and 8 share a common factor of 2.
Step 2: Calculate the least common denominator (LCD) for 14 \frac{1}{4} and 35 \frac{3}{5} .
The LCD of 4 and 5 is 20.
Rewrite 14 \frac{1}{4} as 520 \frac{5}{20} and 35 \frac{3}{5} as 1220 \frac{12}{20} .

Step 3: Subtract the fractions: 1220520=720 \frac{12}{20} - \frac{5}{20} = \frac{7}{20} .

Therefore, the missing fraction needed to satisfy the original equation is 720 \frac{7}{20} .

Thus, the solution to the problem is 720 \frac{7}{20} .

3

Final Answer

720 \frac{7}{20}

Key Points to Remember

Essential concepts to master this topic
  • Rule: Simplify fractions first before finding common denominators
  • Technique: LCD of 4 and 5 is 20: 14=520 \frac{1}{4} = \frac{5}{20} , 35=1220 \frac{3}{5} = \frac{12}{20}
  • Check: Verify by substituting: 14+720=520+720=1220=35 \frac{1}{4} + \frac{7}{20} = \frac{5}{20} + \frac{7}{20} = \frac{12}{20} = \frac{3}{5}

Common Mistakes

Avoid these frequent errors
  • Not simplifying fractions before starting
    Don't work with 28 \frac{2}{8} directly = complicated calculations with LCD of 40! This makes the problem much harder than needed. Always simplify fractions first: 28=14 \frac{2}{8} = \frac{1}{4} gives easier LCD of 20.

Practice Quiz

Test your knowledge with interactive questions

Solve the following exercise:

\( \frac{3}{9}+\frac{1}{9}=\text{?} \)

FAQ

Everything you need to know about this question

Why do I need to simplify 28 \frac{2}{8} first?

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Simplifying makes the problem much easier! Working with 14 \frac{1}{4} instead of 28 \frac{2}{8} gives you a smaller LCD (20 instead of 40) and simpler arithmetic.

How do I find the LCD of 4 and 5?

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Since 4 and 5 share no common factors (they're relatively prime), multiply them together: 4 × 5 = 20. This is your LCD!

What does the ? represent in this equation?

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The ? represents the missing addend - the fraction you need to add to 28 \frac{2}{8} to get 35 \frac{3}{5} . Think of it like: ? = 3528 \frac{3}{5} - \frac{2}{8}

Can I convert to decimals instead?

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You could, but it's not recommended here! 35=0.6 \frac{3}{5} = 0.6 and 14=0.25 \frac{1}{4} = 0.25 , but 720=0.35 \frac{7}{20} = 0.35 is harder to recognize. Stick with fractions for exact answers.

How do I check if 720 \frac{7}{20} is in simplest form?

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Find the GCD of 7 and 20. Since 7 is prime and doesn't divide 20, the GCD is 1. This means 720 \frac{7}{20} is already in simplest form!

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