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starMay 2013

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This is where you'll find the latest happenings, news, & ideas in math teaching

Math teaching videos
My videos at YouTube show you how to teach concepts.
How to help students with multiplication tables?


Worksheets
Various worksheets on TONS of math topics you can generate for free!

Basic operations worksheet generator is updated! Make worksheets for whole numbers or integers - all four operations, including add & subtract or multiply & divide - horizontal or vertical - add a border and/or extra workspace, use a variable, and more.

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Learn how to TEACH concepts or about general concerns in math education.

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A list of free message boards, math help websites, and online tutoring services.

Fun and games
I have two games on my site, plus links to many.
Game: Choose Math Operation
Word guess game (easy hangman)
Word guess game (difficult)


Multiplying fractions by whole numbers
Free lesson with a video

In the video below (also available at my Youtube channel), I teach multiplying fractions by whole numbers, which is a fairly easy concept. Students just need to remember that 4 x (2/3) is not calculated as (4 x 2) / (4 x 3). In the visual model, you can color two thirds, four times, to get the answer. Doubling or tripling recipes is a nice application of this concept.

I also show an interesting connection between (1/3) x 5 or one-third of five pies, and 5 x (1/3), or five copies of 1/3.


1. a. Color first 

3

8

.  Color another 

3

8

.  Continue
        till you have colored five times 

3

8

 .
 
      5 ×  

3

8

 =
[available in the book]
    c. Color five times 

7

12

 .
 
       5 ×  

7

12

 =
 
    e. [available in the book]

 

Multiplication of whole numbers can be solved by repeated addition:

  5 × 4  =  4 + 4 + 4 + 4 + 4  = 20              3 × 120  =  120 + 120 + 120  = 360

Multiplying a fraction by a whole number can be solved the same way:

3 ×

1

4

  =  

1

4

 + 

1

4

 + 

1

4

  =  3

4

5 ×

2

9

  =  

2

9

 + 

2

9

 + 

2

9

 + 

2

9

 + 

2

9

  = 

10

9

  =  1

1

9

2. Write the multiplication problems as addition problems and solve. Remember to give your answer as a mixed number and simplify the fractional parts to lowest terms whenever possible.

 a.  5 ×

1

4

=
 
   
  f. [available in the book]


3. Solve. Can you find a SHORTCUT where you don't have to solve these by actually adding?

 a.   3 ×

2

9

     
     
h.   3 ×

3

10

 The shortcut is (explain) __________________________________________________________

____________________________________________________________
 

We know multiplication can be done in any order.
In other words, multiplication is commutative.
So, 5 ×

3

8

 is the same as 

3

8

× 5.  Both equal 

15

8

or 1

7

8

.

4. Multiply.

  a.   5 ×

7

9

[available in the book]    
     
h.  

12

17

  × 10

 

A fraction of a number is the same as that fraction TIMES the number. 
In other words, the word 'of ' translates into multiplication. For example:

3

7

of 14  is

3

7

× 14. You can solve this by multiplying 14 ×

3

7

  = 

42

7

 = 6.

 

5. a.  Marlene wants to cut down on sugar - so she decided to
         only use 2/3 of the amount of sugar mentioned in the
         recipe. How much sugar will she need?
 

    b.  [available in the book]

 
Brownies

1/2 C butter
2 C brown sugar
4 eggs
12 tbsp cocoa powder
2 cups flour
1 tsp vanilla




The ideas in this fraction lesson are taken from the Math Mammoth Fractions 2 book. Only a few examples of each problem type are shown; you should make more problems of each kind for the student.

Math Mammoth Fractions 2
A self-teaching worktext that teaches fractions using visual models, a sequel to Math Mammoth Fractions 1. The book covers simplifying fractions, multiplication and division of fractions and mixed numbers, converting fractions to decimals, and ratios.

Available as an affordable download ($5.00), and also as a printed copy.

=> Learn more and see the free samples!

See more topical Math Mammoth books


Next lesson: Multiplying fractions by fractions




Practice makes perfect. Practice math at IXL.com

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Practice makes perfect. Practice math at IXL.com


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