vulgar fractions -3

Did you know... Your brain gets better the more you use it.

III. ( 10.10.2013)

http://www.teachertube.com/viewVideo.php?video_id=9995

http://www.teachertube.com/viewVideo.php?video_id=10060

http://www.teachertube.com/viewVideo.php?video_id=91046

https://www.khanacademy.org/math/arithmetic/fractions/Adding_and_subtracting_fractions/v/subtracting--fractions

Subtracting Fractions

There are 3 simple steps to subtract fractions

·  Step 1. Make sure the bottom numbers (the denominators) are the same

·  Step 2. Subtract the top numbers (the numerators). Put the answer over the same denominator.

·  Step 3. Simplify the fraction (if needed).

Subtracting Fracion with Like Denominators

Example 1:

3 / – / 1
4 / 4

Step 1. The bottom numbers are already the same. Go straight to step 2.

Step 2. Subtract the top numbers and put the answer over the same denominator:

3 / – / 1 / = / 3–1 / = / 2
4 / 4 / 4 / 4


Step 3. Simplify the fraction:

2 / = / 1
4 / 2

Example 2:

1 / – / 1
2 / 6

Step 1. The bottom numbers are different. See how the slices are different sizes? We need to make them the same before we can continue, because wecan'tsubtract them like this:

1/2 / − / 1/6 / = / ?

To make the bottom numbers the same, multiply the top and bottom of the first fraction (1/2) by3like this:

× 3
1 / = / 3
2 / 6
× 3

And now our question looks like this:

3/6 / − / 1/6

The bottom numbers (the denominators) are the same, so we can go to step 2.

Step 2. Subtract the top numbers and put the answer over the same denominator:

3 / – / 1 / = / 3–1 / = / 2
6 / 6 / 6 / 6

In picture form it looks like this:

3/6 / − / 1/6 / = / 2/6

Step 3. Simplify the fraction:

2 / = / 1
6 / 3

Making the Denominators the Same https://www.khanacademy.org/math/arithmetic/fractions/Adding_and_subtracting_fractions/v/subtracting-fractions-with-unlike-denominators

In the previous example it was easy to make the denominators the same, but it can be harder ... so you may need to use either the

·  Common Denominator Method, or the

·  Least Common Denominator Method

They both work, use whichever you prefer!

Example: Cupcakes You are going to sell cupcakes at a market:

·  You get paid2/5of total sales

·  But you have to pay1/4of total sales for the market stall

How much do you get? We need to subtract1/4from2/5

2 / − / 1 / = / ?
5 / 4 / ?

Firstmake the bottom numbers (the denominators) the same.

Multiply top and bottom of2/5by4:

2 ×4 / − / 1 / = / ?
5 ×4 / 4 / ?

And multiply top and bottom of1/4by5:

2 × 4 / − / 1 ×5 / = / ?
5 × 4 / 4 ×5 / ?

Nowdo the calculations:

8 / − / 5 / = / 8−5 / = / 3
20 / 20 / 20 / 20

Answer: you get to keep3/20of total sales.

Subtraction part from whole

Sometimes a mixed number is subtracted from a whole number. In this case, you can also rewrite the whole number as a mixed number in order to perform the subtraction. You use an equivalent mixed number that has the same denominator as the fraction in the other mixed number.

Example
Problem / / Subtract. Simplify the answer and write as a mixed number.




7 – 4 = 3
/ Regroup one from the whole number and write it as.
Rewrite the subtraction expression using the equivalent fractions.
Subtract the whole numbers, subtract the fractions.
/ Combine the whole number and the fraction.
Answer /

Subtracting Mixed Numbers with Like Denominators

Subtracting Mixed Numbers

If the fractional part of the mixed number being subtracted is larger than the fractional part of the mixed number from which it is being subtracted, or if a mixed number is being subtracted from a whole number, follow these steps:

1.Subtract 1 from the whole number part of the mixed number being subtracted.

2.Add that 1 to the fraction part to make an improper fraction. For example,.

3.Then, subtract as with any other mixed numbers.

Alternatively, you can change both numbers to improper fractions and then subtract.

I. play

http://www.sheppardsoftware.com/mathgames/fractions/mathman_add_subtract_fractions.htm

II. exercises http://www.dadsworksheets.com/v1/Worksheets/Fraction%20Subtraction.html

Summary

Subtracting fractions and mixed numbers combines some of the same skills as adding whole numbers and adding fractions and mixed numbers. When subtracting fractions and mixed numbers, first find a common denominator if the denominators are not alike, rewrite each fraction using the common denominator, and then subtract the numerators. When subtracting mixed numbers, if the fraction in the second mixed number is larger than the fraction in the first mixed number, rewrite the first mixed number by regrouping one whole as a fraction. Alternatively, rewrite all fractions as improper fractions and then subtract. This process is also used when subtracting a mixed number from a whole number.