Adding and subtracting algebraic fractions

Two lessons (at least).

Includes quite simple ones…

Has a task that worked really well with my class. Write the missing step. Cognitive load and that.

Plus some questions.

Goes onto more complicated examples and exercises.

As an aside, I posted a picture from this resource on Twitter and it got (at the time of reading) close to 200 likes and I ended up picking up about 50 new followers.

Which I don’t quite get. Normally my stuff gets 0-20 likes despite being pretty similar. I don’t understand social media at all.

One Comment

1. Anne Santiago

Hi Richard, your post and your samples are very helpful in practicing algebraic fraction. The student would find this not so difficult if they master the basic of fraction. So let me also share my idea on dealing with fractions.

To add and subtract fractions successfully is to make the rules stick to your memory.

Rules are:
Same denominator:
Add both numerators then reduce. The result would be the final answer.
Different denominator (4 steps):
1. Multiply the numerator of first fraction to the denominator of second fraction. The result is the new numerator of first fraction.
2. Multiply the numerator of the second fraction to the denominator of first fraction. The result is the new numerator of second fraction.
3. Multiply both denominators. The result is the common denominator for two fractions.
4. Add the two new numerators. The result is the answer.

To make it stick to your memory:
Rules for subtraction:
Same denominator:
Subtract second numerator from first then reduce. The result would be the final answer.
Different denominator (4 steps):
1. Multiply the numerator of first fraction to the denominator of second fraction. The result is the new numerator of first fraction.
2. Multiply the numerator of the second fraction to the denominator of first fraction. The result is the new numerator of second fraction.
3. Multiply both denominators. The result is the common denominator for two fractions.
4. Subtract new second numerator from first new numerator. The result is now the answer.

To make it stick to your memory:
Same numerator:
Add two fractions 50 times.
Subtract two fractions 50 times.
Different denominator:
Add two fractions 100 times.
Subtract two fractions 100 times.

To check if your answer is right and your step by step solution is correct:
Use fraction calculator with button from http://www.fractioncalc.com. It is important that you follow the correct steps in adding unlike fraction. Unlike fractions are those fractions with different denominator.

The key here is to make the rules implanted into the minds of the students so that they will never forget.

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