Engaging students: Adding and subtracting decimals

In my capstone class for future secondary math teachers, I ask my students to come up with ideas for engaging their students with different topics in the secondary mathematics curriculum. In other words, the point of the assignment was not to devise a full-blown lesson plan on this topic. Instead, I asked my students to think about three different ways of getting their students interested in the topic in the first place.

I plan to share some of the best of these ideas on this blog (after asking my students’ permission, of course).

This student submission comes from my former student Daniel Herfeldt. His topic, from Pre-Algebra: adding and subtracting decimals.

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How could you as a teacher create an activity or project that involves your topic?

A great engage activity that I have thought about as a teacher would be to have the students add and subtract money. For this activity I would provide the students with play money (dollar bills, quarters, dimes, nickels, and pennies) needed to proceed. I would then ask the students to show me what 65 cents looks like. Most outcomes will probably look similar with two quarters, a dime, and a nickel while in fact there are many ways to show what 65 cents looks like. Some students might come up with a quarter and four dimes, or 13 nickels. After the students finish with their first example, I would ask them if they could find another way to add up the coins to get 65 cents. This is a very simple activity that refreshes the students’ knowledge on how to add decimals. The activity also shows the teacher which students have a harder time with the topic.



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How was this topic appeared in pop culture?

The concept of adding and subtracting decimals is all over the world. It is used for everyday things, such as sports. One of the most watched things on television is the summer or winter Olympics. People from all over the world compete in several events and get scores. For example, gymnasts compete for the highest score in the specific event they are doing and then add it to their total score to be declared the winner. After the first event, one gymnast may have the highest score of 16.543 while the person below her has a score of 15.785. Then in the second event, the person that previously had a higher score only scored 12.400, while the person that was behind her scored a 15.115. To declare the winner of the two, you would have to sum up both scores and see which of the two competitors had the higher score. You would get the total of 28.943 for the first gymnast, and 30.900 for the second. From here the winner would be the second gymnast.



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How can technology be used to effectively engage students with this topic?


This game would be a great tool to refresh a students’ memory on how to add decimals if you are planning to have a test. To start, you would hand out every student their own small whiteboard and marker. You would then put the game on the projector screen so that all of the students can see it. Start out with clicking the easy button so that you don’t start with a difficult problem. Ex: 31 + .4. This should be a problem that all students can answer. Have all the students write down on their own white board what they think the answer would be. After the students finish, ask them to put their white board face down. Once all of the students finish, have everyone raise up their answers. Afterwards plug in the answer that is most common amongst the students to see if the majority was correct. If most are correct, proceed to the next difficulty, which is medium, and repeat the steps that you did for the easy problem. If the majority of the class gets it right, then go to the final and hardest difficulty and repeat the steps one more time. If the majority of the students get the answer wrong for any difficulty, do the problem on the board to show the steps and try another problem of the same difficulty. The students will then remember the steps and have a higher chance of being correct. When the students get the hard problems correct, keep doing the hard problems until you feel the students have grasped the concept.


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