Solve the Fraction Subtraction: 4/5 - 5/10 Step by Step

Fraction Subtraction with Common Denominators

Solve the following equation:

45510= \frac{4}{5}-\frac{5}{10}=

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:05 Let's solve this problem together.
00:08 First, we need to find the least common denominator.
00:12 So, multiply by two, to get the common denominator of ten.
00:17 Remember, multiply both the numerator and the denominator by two.
00:22 Next, let's do the multiplications.
00:25 Then, subtract with the common denominator.
00:29 That's how we find the answer to the problem!

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Solve the following equation:

45510= \frac{4}{5}-\frac{5}{10}=

2

Step-by-step solution

Let's begin by determining the lowest common denominator between 5 and 10.

In order to identify the lowest common denominator, we must find a number that is divisible by both 5 and 10.

In this case, the common denominator is 10

Let's proceed to multiply each fraction by the appropriate number in order to reach the denominator 10.

We'll multiply the first fraction by 2

We'll multiply the second fraction by 1

4×25×25×110×1=810510 \frac{4\times2}{5\times2}-\frac{5\times1}{10\times1}=\frac{8}{10}-\frac{5}{10}

Finally let's subtract as follows:

8510=310 \frac{8-5}{10}=\frac{3}{10}

3

Final Answer

310 \frac{3}{10}

Key Points to Remember

Essential concepts to master this topic
  • LCD Rule: Find the lowest common denominator before subtracting fractions
  • Technique: Convert 45 \frac{4}{5} to 810 \frac{8}{10} by multiplying by 2
  • Check: Verify that 810510=310 \frac{8}{10} - \frac{5}{10} = \frac{3}{10}

Common Mistakes

Avoid these frequent errors
  • Subtracting denominators along with numerators
    Don't subtract 4/5 - 5/10 as (4-5)/(5-10) = -1/-5! This treats fractions like whole numbers and gives completely wrong results. Always find a common denominator first, then only subtract the numerators.

Practice Quiz

Test your knowledge with interactive questions

Without calculating, determine whether the quotient in the division exercise is less than 1 or not:

\( 5:6= \)

FAQ

Everything you need to know about this question

Why can't I just subtract 4-5 and 5-10 directly?

+

Because fractions represent parts of wholes, not separate numbers! You can only subtract fractions when they have the same denominator - like subtracting 3 apples from 8 apples, not 3 apples from 5 oranges.

How do I know which denominator to use as the LCD?

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Look for the smallest number that both denominators divide into evenly. Since 10 ÷ 5 = 2 and 10 ÷ 10 = 1, the LCD is 10!

Do I always multiply the first fraction when finding LCD?

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Not always! Only multiply fractions that don't already have the LCD. In this problem, 510 \frac{5}{10} already has denominator 10, so we leave it alone.

What if I get a different LCD than 10?

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Any common multiple of 5 and 10 works (like 20, 30, 40...), but using the lowest one keeps numbers small and makes calculations easier!

Can this fraction be simplified further?

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310 \frac{3}{10} is already in simplest form because 3 and 10 share no common factors other than 1. Always check if your final answer can be reduced!

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