Modeling Fractions Watch It!
The cupcakes recipe calls for 1/3 cup of butter or margarine. If you are doubling the recipe, then you need to find a way to double 1/3 as well. An area model can help you. The rectangle below has been divided into 3 equal sections, or thirds. Each section is 1/3 of the whole rectangle.
The shaded section is double the size of each 1/3 section. Using addition, you can see 1/3 + 1/3 = 2/3. You also can use multiplication: there are 2 equal sections, each is 1/3, so 2 x 1/3 = 2/3.
Want to see this in action? Click to view the video below to watch a cartoon of two kids talking about how to double 1/3 in a recipe.
| Keyboard Shortcut | Action |
|---|---|
| Space | Pause/Play video playback |
| Enter | Pause/Play video playback |
| m | Mute/Unmute video volume |
| Up and Down arrows | Increase and decrease volume by 10% |
| Right and Left arrows | Seek forward or backward by 5 seconds |
| 0-9 | Fast seek to x% of the video. |
| f | Enter or exit fullscreen. (Note: To exit fullscreen in flash press the Esc key. |
| c | Press c to toggle captions on or off |
Doubling with Fractions
As you go through this lesson, remember that 1/3 + 1/3 and 2 x 1/3 both equal 2/3. Notice that when you add fractions with a common denominator, you add the numerators. What steps do you think you have to take to turn 2 x 1/3 into 2/3? Thinking about the connection between addition and multiplication can help you when you multiply a fraction by a whole number.
