Solve the Fraction Expression: 3/5 - 1/5 + 3/15 Step by Step

Fraction Operations with Different Denominators

3515+315= \frac{3}{5}-\frac{1}{5}+\frac{3}{15}=

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Solve
00:04 Connect the fractions into one fraction
00:19 Multiply by 3 to get a common denominator
00:26 Remember to multiply both numerator and denominator
00:35 Calculate the multiplications
00:45 Add under the common denominator
00:51 Calculate the numerator
00:58 Reduce the fraction as much as possible
01:01 Remember to divide both numerator and denominator
01:04 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

3515+315= \frac{3}{5}-\frac{1}{5}+\frac{3}{15}=

2

Step-by-step solution

To solve this problem, we will follow these steps:

  • Step 1: Find the least common denominator (LCD) for the fractions.
  • Step 2: Convert each fraction to an equivalent fraction with the common denominator.
  • Step 3: Perform the operations in the given order, subtraction first, then addition.

Now, let's work through each step:

Step 1: The denominators of the given fractions are 5 and 15. The least common multiple (LCM) of these numbers is 15, so 15 will be our common denominator.

Step 2: Convert each fraction to have the denominator of 15:
- 35\frac{3}{5} is converted by multiplying both the numerator and denominator by 3, resulting in 915\frac{9}{15}.
- 15\frac{1}{5} is converted by multiplying both the numerator and denominator by 3, yielding 315\frac{3}{15}.
- 315\frac{3}{15} is already in terms of the common denominator.

Step 3: Perform the subtraction and addition:
- Start by subtracting 315\frac{3}{15} from 915\frac{9}{15}:

915315=615\frac{9}{15} - \frac{3}{15} = \frac{6}{15}

Now, add 615\frac{6}{15} and 315\frac{3}{15}:

615+315=915\frac{6}{15} + \frac{3}{15} = \frac{9}{15}

Finally, simplify 915\frac{9}{15} by dividing the numerator and denominator by their greatest common divisor, which is 3:

915=35\frac{9}{15} = \frac{3}{5}

Therefore, the solution to the problem is 35\frac{3}{5}.

3

Final Answer

35 \frac{3}{5}

Key Points to Remember

Essential concepts to master this topic
  • LCD Rule: Find least common denominator for all fractions first
  • Technique: Convert 35 \frac{3}{5} to 915 \frac{9}{15} using LCD of 15
  • Check: Simplify final answer 915=35 \frac{9}{15} = \frac{3}{5} by dividing by GCD ✓

Common Mistakes

Avoid these frequent errors
  • Adding and subtracting fractions with different denominators directly
    Don't calculate 3515+315 \frac{3}{5} - \frac{1}{5} + \frac{3}{15} by mixing denominators = impossible math! You can't combine fractions unless they have the same denominator. Always convert all fractions to the same denominator first using the LCD.

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 and subtract the numerators with different denominators?

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Because fractions represent parts of different-sized wholes! 15 \frac{1}{5} means 1 piece of something cut into 5 parts, while 315 \frac{3}{15} means 3 pieces cut into 15 parts. You need the same size pieces to combine them.

How do I find the LCD of 5 and 15?

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List the multiples: 5: 5, 10, 15, 20... 15: 15, 30, 45... The smallest number that appears in both lists is 15, so that's your LCD!

What if I get the LCD wrong?

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You'll still get the right answer eventually, but it will take more steps! Using a common denominator that's not the least just means bigger numbers that you'll need to simplify later.

Do I always need to simplify my final answer?

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Yes! Always check if you can reduce your fraction. Divide both numerator and denominator by their greatest common divisor. In this problem, 915 \frac{9}{15} simplifies to 35 \frac{3}{5} .

Can I work from left to right instead of finding LCD first?

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You could, but it's much harder! You'd have to find a common denominator for the first two fractions, then find another common denominator with the third. The LCD method is faster and less error-prone.

What if the problem has more than three fractions?

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Same process! Find the LCD of all denominators, convert every fraction, then add and subtract from left to right. The method works for any number of fractions.

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