Friday, March 6, 2009

Subtracting Unlike Fractions.

Today's lesson was on "How to subtract unlike fractions".
The first task began by asking pupils to group 24 marbles equally.
Here are some of the student's way of grouping 24 marbles written on their mini-journal.


The objective of this activity is to lead them to understand that though fractions can be different, the total value remains the same. This goes to show that by manipulating fraction numbers, we are only manipulating their numerators and denominators and not their value.

Here's another "proof" shown below.

Understanding this concept will help students remember how to manipulate fractions when dealing with unlike fractions.


Students attempting the questions of adding and subtracting unlike fractions..


I was pleased to hear another student coming up with another variation of converting the denominators to a common multiple. (shown above). I quickly used the chance to explain that though using a different multiple may be different initially, the end result will be the same. I was so excited in proving this that I nearly forget to mention that one must always simplify fractions into simplest form whenever possible.

Guess I better inform the class for the next lesson.

Mr Xie.

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