Solve the Fraction Addition: 4/15 + 2/5 Step by Step

Fraction Addition with Common Denominators

415+25= \frac{4}{15}+\frac{2}{5}=

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:06 Let's solve this problem together.
00:09 We need to find the smallest number both fractions share as a denominator.
00:14 So, we multiply the denominators by three to make them the same.
00:18 Remember everyone, multiply both the top number— that's the numerator—and the bottom number—the denominator.
00:25 Now, let's do those multiplications. You can do it!
00:30 Good! Put the results under the same denominator.
00:35 Time to add the numerators. Almost there!
00:41 Let's reduce the fraction by dividing both top and bottom numbers by the greatest common factor.
00:47 Don't forget to divide both the numerator and the denominator.
00:51 Great job! And that's how you solve the question. Well done!

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

415+25= \frac{4}{15}+\frac{2}{5}=

2

Step-by-step solution

To solve the problem 415+25 \frac{4}{15} + \frac{2}{5} , we will add these fractions by finding a common denominator.

Step 1: Find the Least Common Denominator (LCD).
The denominators are 15 and 5. The LCM of 15 and 5 is 15, as 15 is already a multiple of 5.

Step 2: Convert each fraction to have the same denominator, 15.
- The fraction 415 \frac{4}{15} already has the denominator 15. - Convert 25 \frac{2}{5} to a fraction with a denominator of 15 by multiplying both the numerator and denominator by 3: 2×35×3=615 \frac{2 \times 3}{5 \times 3} = \frac{6}{15} .

Step 3: Add the fractions with common denominators.
Now we have: 415+615 \frac{4}{15} + \frac{6}{15} .
Add the numerators: 4+6=10 4 + 6 = 10 .
The new fraction is 1015 \frac{10}{15} .

Step 4: Simplify the resulting fraction, if possible.
Both 10 and 15 are divisible by 5.
Divide the numerator and the denominator by their greatest common divisor (GCD), which is 5: 10÷515÷5=23 \frac{10 \div 5}{15 \div 5} = \frac{2}{3} .

The solution to the problem is 23 \frac{2}{3} .

3

Final Answer

23 \frac{2}{3}

Key Points to Remember

Essential concepts to master this topic
  • Rule: Find the least common denominator before adding fractions
  • Technique: Convert 25 \frac{2}{5} to 615 \frac{6}{15} by multiplying by 3
  • Check: Simplify 1015 \frac{10}{15} by dividing both parts by 5 ✓

Common Mistakes

Avoid these frequent errors
  • Adding numerators and denominators separately without finding common denominator
    Don't add 415+25 \frac{4}{15} + \frac{2}{5} as 620 \frac{6}{20} by adding 4+2 and 15+5! This gives a completely wrong answer because you're adding parts of different-sized wholes. Always find the LCD first and convert both fractions.

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 directly?

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You can only add fractions when they have the same denominator! Think of it like adding pieces of different-sized pies - you need to cut them into same-sized pieces first.

How do I find the least common denominator quickly?

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Look for the larger denominator first. If it's divisible by the smaller one (like 15 ÷ 5 = 3), then the larger number is your LCD! Otherwise, multiply the denominators together.

Do I always need to simplify my final answer?

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Yes, always simplify! Look for the greatest common divisor of the numerator and denominator. In this case, both 10 and 15 divide by 5 to give 23 \frac{2}{3} .

What if one fraction already has the common denominator?

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Perfect! Like 415 \frac{4}{15} in this problem - you can leave it as is and only convert the other fraction. This saves you work!

How can I check if my answer is correct?

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Convert your answer back to a decimal and add the original fractions as decimals: 4150.267 \frac{4}{15} ≈ 0.267 and 25=0.4 \frac{2}{5} = 0.4 , so 0.267 + 0.4 = 0.667, which equals 23 \frac{2}{3}

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