Solve: 3/5 + 1/5 - 3/15 Fraction Operation Challenge

Fraction Operations with Mixed Denominators

35+15315= \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
00:08 Connect the fractions into one fraction
00:21 Multiply by 3 to get a common denominator
00:26 Remember to multiply both numerator and denominator
00:35 Calculate the multiplications
00:41 Combine under the common denominator
00:49 Calculate the numerator
00:56 Reduce the fraction as much as possible
01:00 Remember to divide both numerator and denominator
01:03 And this is the solution to the problem

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

35+15315= \frac{3}{5}+\frac{1}{5}-\frac{3}{15}=

2

Step-by-step solution

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

  • Step 1: Determine a common denominator for the fractions.
  • Step 2: Convert each fraction to have this common denominator.
  • Step 3: Perform the addition and subtraction operations on these fractions.
  • Step 4: Simplify the resulting fraction, if possible.

Now, let's work through each step:

Step 1: To combine 35 \frac{3}{5} , 15 \frac{1}{5} , and 315 \frac{3}{15} , identify the least common denominator (LCD). The denominators here are 5, 5, and 15. The least common multiple of 5 and 15 is 15. Therefore, our common denominator is 15.

Step 2: Convert each fraction to an equivalent fraction with a denominator of 15:
35=3×35×3=915\frac{3}{5} = \frac{3 \times 3}{5 \times 3} = \frac{9}{15},
15=1×35×3=315\frac{1}{5} = \frac{1 \times 3}{5 \times 3} = \frac{3}{15},
315\frac{3}{15} is already with the common denominator.

Step 3: Add and subtract the fractions:
915+315=1215 \frac{9}{15} + \frac{3}{15} = \frac{12}{15}
1215315=915 \frac{12}{15} - \frac{3}{15} = \frac{9}{15} .

Step 4: Simplify the resulting fraction:
915=35\frac{9}{15} = \frac{3}{5} (dividing the numerator and denominator by their greatest common divisor, which is 3).

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
  • Common Denominator: Find LCD to add and subtract different denominators
  • Technique: Convert 35=915 \frac{3}{5} = \frac{9}{15} by multiplying by 33 \frac{3}{3}
  • Check: Simplify final answer by dividing numerator and denominator by GCD ✓

Common Mistakes

Avoid these frequent errors
  • Adding denominators together instead of finding LCD
    Don't add 5 + 5 + 15 = 25 as the denominator! This creates incorrect fractions that don't represent the original values. Always find the LCD (15) and convert each fraction to equivalent fractions with that common denominator.

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 separately?

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Because fractions represent parts of different wholes! 35 \frac{3}{5} and 315 \frac{3}{15} are parts of different-sized wholes. You must convert them to the same-sized pieces first.

How do I find the LCD of 5 and 15?

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

What if my final answer is an improper fraction?

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That's okay! In this problem, 915 \frac{9}{15} simplifies to 35 \frac{3}{5} , which is proper. Always simplify by dividing both numerator and denominator by their greatest common factor.

Can I work left to right without finding LCD first?

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You could add 35+15=45 \frac{3}{5} + \frac{1}{5} = \frac{4}{5} first, but you'll still need LCD to subtract 315 \frac{3}{15} . It's usually more efficient to find the LCD once and convert everything at the start.

How do I know when my fraction is fully simplified?

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A fraction is simplified when the numerator and denominator share no common factors except 1. For 915 \frac{9}{15} , both are divisible by 3, so divide: 9÷315÷3=35 \frac{9÷3}{15÷3} = \frac{3}{5} .

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