Solve the Fraction Addition: 1/5 + 7/10 Step by Step

Fraction Addition with Common Denominators

Solve the following exercise:

15+710=? \frac{1}{5}+\frac{7}{10}=\text{?}

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Solve
00:03 Multiply the fraction by 2 to find a common denominator
00:09 Remember to multiply both numerator and denominator
00:17 Calculate the multiplications
00:22 Add under common denominator
00:26 Calculate the numerator
00:30 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:

15+710=? \frac{1}{5}+\frac{7}{10}=\text{?}

2

Step-by-step solution

To solve the problem of adding the fractions 15\frac{1}{5} and 710\frac{7}{10}, we follow these steps:

  • Step 1: Identify the least common multiple (LCM) of the denominators 5 and 10, which is 10.
  • Step 2: Convert 15\frac{1}{5} to a fraction with a denominator of 10. To do this, multiply both the numerator and denominator by 2: 15=1×25×2=210 \frac{1}{5} = \frac{1 \times 2}{5 \times 2} = \frac{2}{10}
  • Step 3: Observe that 710\frac{7}{10} already has the common denominator of 10.
  • Step 4: Add the two fractions with a common denominator: 210+710=2+710=910 \frac{2}{10} + \frac{7}{10} = \frac{2 + 7}{10} = \frac{9}{10}

The sum of 15\frac{1}{5} and 710\frac{7}{10} is thus 910\mathbf{\frac{9}{10}}.

3

Final Answer

910 \frac{9}{10}

Key Points to Remember

Essential concepts to master this topic
  • Common Denominator Rule: Find LCM of denominators before adding fractions
  • Conversion Technique: Transform 15 \frac{1}{5} to 210 \frac{2}{10} by multiplying by 22 \frac{2}{2}
  • Verification Check: Convert answer back: 910=210+710 \frac{9}{10} = \frac{2}{10} + \frac{7}{10}

Common Mistakes

Avoid these frequent errors
  • Adding numerators and denominators separately
    Don't add 15+710 \frac{1}{5} + \frac{7}{10} as 1+75+10=815 \frac{1+7}{5+10} = \frac{8}{15} ! This completely ignores fraction rules and gives wrong answers. Always find a common denominator first, then add only the numerators.

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 tops and bottoms separately?

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Because fractions represent parts of different wholes! Adding 15 \frac{1}{5} (fifths) to 710 \frac{7}{10} (tenths) is like adding apples to oranges. You need the same denominator to combine them properly.

How do I find the least common multiple of 5 and 10?

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List the multiples: 5 → 5, 10, 15, 20... and 10 → 10, 20, 30... The smallest number that appears in both lists is 10. Since 10 is already a multiple of 5, the LCM is 10!

What if both fractions need to be converted?

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Convert both fractions to have the common denominator! For example, with 23+14 \frac{2}{3} + \frac{1}{4} , convert both to twelfths: 812+312=1112 \frac{8}{12} + \frac{3}{12} = \frac{11}{12} .

Do I need to simplify my final answer?

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Always check if you can simplify! In this problem, 910 \frac{9}{10} is already in lowest terms since 9 and 10 share no common factors besides 1.

What's the quickest way to check if my answer is right?

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Convert your answer to a decimal and check: 15=0.2 \frac{1}{5} = 0.2 and 710=0.7 \frac{7}{10} = 0.7 , so 0.2 + 0.7 = 0.9 = 910 \frac{9}{10}

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