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Comparing and Ordering Decimals

As crazy as it sounds and as bad as I hate to admit it, I had never taught using Base 10 Blocks. No teacher had ever taught me using them, and when I taught 9th grade algebra the books never talked about them. It wasn’t until I started teaching 6th grade math that I was introduced. Needless to say, I’ll never teach decimals without base 10 blocks again. Last year I made the base 10 blocks out of paper. For this year, I ordered plastic blocks and what a great investment!

For teaching “comparing and ordering decimals”, I used a couple of different resources. The first resource I used was the “Hands-On Math!” book. There is a review of this book in my “Resource” tab.

Day 1:

Activity 1: “Match Up”:

 I placed the students in pairs. I gave each pair a set of base 10 blocks that I had prepared ahead of time. 4 flats, 18 rods, 18 small cubes. I explained base 10 blocks and that 1 flat was equal to a whole, that it took 10 rods to make up a whole so the rod is .1 of a whole, and that it takes 100 small cubes to make up a flat so a small cube is .01. I then wrote the numbers 2.34 and 2.61 on the board and told the groups to build those numbers with their blocks. The first time took a little help for some of the groups, but they quickly caught on. I explained that in order to compare them that they had to start with the largest blocks first. Both numbers had two flats. They then move on to the rods and compare them. Six is more than three, therefore 2.34 < 2.61. I put up another few problems as in 1.8 and 1.75, 0.95 and 1.3.

Activity 2: Count to Match:

This activity moves from the concrete materials to drawing pictures. This process helps them transition to the more abstract action of comparing decimals without the help of manipulatives. Still in partners, I have the students get out a sheet of paper and I write the decimals 4.35 and 4.38 on the board. I ask the students to each draw the models of those numbers using the following symbols: 

Starting with the largest place value, they are to begin marking out the symbols the two numbers have in common until they have a set of blocks that are not equal and circle those that are left over. Do this a couple of more times with numbers such as 3.8 and 3.75, 0.98 and 1.2, and 5.04 and 5.

Activity 3: Who Has More?

This is the “game” activity that the students will play. The activity in the book has them continue to use the base 10 blocks, but I didn’t feel my students still needed that help. I kept the groups in pairs for this game as well. The book suggests to put them in teams of four and have them pair up. I suppose if I taught younger students, I would maybe do this but my students worked just as easily by themselves. The students were to each have a piece of paper and draw a line down the middle and put their names at the top of each side in order to keep score. I gave each student a ten sided dice numbered 0-9.

They were to each roll their dice three times to form a decimal number. I had them use 0 as their whole number each time. The first roll was the tenths place, second roll was the hundredths place, and the final roll was the thousandths place. They were to write their numbers down in the respective column and compare them and circle the larger number. They played this until I called time.

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