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Welcome to my math blog! The purpose of this blog is to help you stay informed about our learning and experiences that have taken place during our math class. I have also included links your child (and you) may want to use in order to supplement math learning in 5th grade.

Tuesday, October 13, 2015

Order of Operations: PEMDAS and the Power of Parentheses

To introduce our new topic, I asked the kids to write the following math problem on their desk (using dry erase markers):

3 + 3 x 4 + 2 x 3 + 3

After simplifying the expression we shared our answers to find, to our surprise, we had lots of different answers.  I explained that I had forgotten to add a piece of important information.... the parentheses.

I added in the parentheses and the classes reminded me that we do the operation within the parentheses first, so we simplified the expression

3 + (3 x 4) + 2 x (3 + 3)

to find that we had found more answers that did not match.  I explained that the addition of the parentheses changes the rule of how to solve the problem.  I asked whether they thought changing the placement of our grouping symbols would lead to more differing answers.  To test their theory, I asked the students to use the exact same expression, but move the parentheses.

Low and behold, more differing answers!  It was at this point that I asked the students why having all of these differing answers was a problem.  They all agreed that the whole point was for everyone to get the same answer.  I then explained that the reason we were getting a variety of answers was due to the fact that we were not following the set of RULES mathematicians had devised years ago called the Order of Operations.

I then explained that there are universal themes in math and the one we would be focusing on over the next few days was the theme of Order:

Then, I explained to the classes the agreed upon order of operations:  parenthesis, exponents, multiply/divide, then add/subtract.  I found another blog whose teacher used the hopscotch method in her classroom and then created the PEMDAS graphic organizer that we used in class today.  The video with information is at:  

I discussed that we need many different ways to help us remember the Order of Operations.   At this point, I mentioned the acronym PEMDAS.  I also encouraged them to use a mnemonic device to remember the steps such as:

To finish our lesson, I asked the students to answer the following prompt:

I did explain that they were not to simplify the expression.  They were just to explain whether changing the rule (PEMDAS, addition or subtraction of parentheses) would result in a different answer.

Finally, we worked on a Countdown to STAAR.  We have set our +10 goal for the year and know which math categories we need to focus on to reach our goal.  

Tomorrow we will begin graphing the results from our Coundown to STAAR to begin monitoring our successes towards our goal.

Parents can view these documents by going to classroom.google.com and having their child login and then go to their math class.

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