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### Course: 4th grade (2018 edition)>Unit 3

Lesson 4: Comparing fractions with unlike denominators

# Comparing fractions review

Review comparing fractions with common denominators, and try some practice problems.

## Comparing fractions

We can compare fractions by seeing which one takes up a greater portion of the same whole.

### Comparing fractions using common denominators

Let's look at an example.
Compare.
start fraction, 3, divided by, 4, end fraction __ start fraction, 5, divided by, 10, end fraction
Let's change the fractions to have a common denominator of 20: (Want to review common denominators? Check out this article.)
$\begin{array}{rcl}\frac{3}{4}×\frac{5}{5}& =& \frac{15}{20}\\ \\ \frac{5}{10}×\frac{2}{2}& =& \frac{10}{20}\end{array}$
Now that our fractions have the same denominator, we compare their numerators:
start color #11accd, 15, end color #11accd, is greater than, start color #1fab54, 10, end color #1fab54
start color #11accd, start fraction, 15, divided by, 20, end fraction, end color #11accd, is greater than, start color #1fab54, start fraction, 10, divided by, 20, end fraction, end color #1fab54
start color #11accd, start fraction, 3, divided by, 4, end fraction, end color #11accd, is greater than, start color #1fab54, start fraction, 5, divided by, 10, end fraction, end color #1fab54

## Practice

Problem 1
• Current
Compare.
start fraction, 1, divided by, 3, end fraction __ start fraction, 6, divided by, 8, end fraction

Want to try more problems like this? Check out this exercise.

## Want to join the conversation?

• Why do people always use rectangles, pizzas or circles to compare fractions to decimals or fractions alone?
• I agree with Benny C because we see pizzas all the time and our desks are rectangles.
BUT DON'T GO AROUND VISULIZIN' PIZZAS DON'T EAT ZEM EITHER
(1 vote)
• you can remember comparing fractions by cross multiplying like this 3/5 ----- 5/3
5x5=25 and 3x3=9 so you know that 5/3 is bigger !
• Another way is to notice that the numerator is greater than the denominator in 5/3 but not in 3/5!
• Do you have to do it or can you just look at the halves?
• cross multiplying is an easier and faster way to do it. All you do is multiply one denominator by the numerator on the other fraction and put that number next to it and which ever side is bigger that fraction is greater. But remember MULTIPLY UP!
(1 vote)
• Can you compare mixed numbers with unlike denominators?
• Yes you can! Those problems will probably come in 4th and 5th grade. For example, 1/2 + 2 3/4 is a real problem. It equals 3 1/4.
• why the big number is bigger than the smaller one.