Fraction Unit
by Caiti and Jalynne
Adding Fractions - The Clock Model
Bench Marks
1/2 = 30 minutes
1/3 = 20 minutes
1/4 = 15 minutes
1/6 = 10 minutes
1/12 = 5 minutes
These are the most common fractions to use, and are also the simplest fractions to remember because they're all unit fractions!
Examples of adding fractions using the clock model;
1.) 1/2 + 1/3 = 30 minutes + 20 minutes = 50 minutes = 50/60 or 5/6
2.) 2/3 + 1/4 = 40 minutes + 15 minutes = 55 minutes = 55/60 or 11/12
You can also use or even draw a model of a clock to divide into whatever the desired denominator is, for example, you can take your clock and split it into a half and you can see that by the numbers that it is 30 minutes. How easy is that?!
Adding Fractions - Lowest Common Multiples
Adding Fractions- The Money Model
Bench Marks
1/4= 25 cents
1/2= 50 cents
1/5= 20 cents
1/10= 10 cents
1 whole= $1
Examples
1/2 + 1/10= 50 cents + 10 cents= 60 cents= 60/100 or 3/5
1 + 2/5= 100 cents or one dollar + 40 cents= 140 cents or $1.40=1 40/100 or 1 2/5
Equivalent Fractions
These are all equivalent fractions.
Multiplying Fractions
Examples
2/4 x 5/6= 10/24 or 5/12
3/5 x 1/3= 3/15 or 1/5
Dividing Fractions
Examples
4 ÷ 1/4= 1
1/3 ÷ 2/6= 1/3 x 6/2= 6/6 or 1 whole
2 ÷ 1/6= 3
2/5 ÷ 1/2= 2/5 x 2/1= 4/5
Subtracting Fractions
If both fractions already have the same denominator, just subtract the numerators and keep the denominator the same.
Examples
Lowest common multiple is 15~ 4/5 - 2/3= 4x3/5x3- 2x5/3x5= 12/15 -10/15= 2/15
3/5 - 4/10= 3x2/5x2 - 4/10= 6/10 - 4/10= 2/10 or 1/5
Reducing Fractions
Examples
30/60= 15/30= 3/6= 1/2
20/60= 10/30= 5/15= 1/3
15/25= 3/5
24/32= 12/16=6/8=3/4