Curriculum Focus: Decimal Dials

There are two tricks that will help students master this exercise:

1) USE THE METER, RULER, AND ALL OF THE DIALS TO REPRESENT THE TARGET NUMBER

Think of the ruler and the meter as two different visual representations of the target number. The ruler shows where the target number fits on a vertical number line. It is helpful to think of the meter like a mileage meter in a car. If the number has not passed the mark in the middle of the meter line, then you should consider that number on the meter as the previous number.

Take a look at the example below:

 



2) STUDENTS CAN USE ANY DIAL TO HELP THEM ACCURATELY REPRESENT THE TARGET NUMBER

After students are comfortable understanding how the dials, ruler, and meter work together, they can get more creative with the way they use the dials. You may observe students running out of "adjustments" while playing the game. When using dials to build a number like 8.75, most beginning users think that each dial controls a place value separate from the others. For example, they will move the Ones dial chronologically to select the whole number and then they will focus on the Tenths dial. The key is that any dial can be used to represent the target number and that, as users adjust one dial, they all move together. 

For example, to get to 8.75, a user could spin the Ones dial 8.75 times, which is difficult to do accurately, or spin the Hundredths dial 875 times, which is incredibly time consuming. Ask students who are struggling with using the dials to spin one dial and watch what happens with the others. Discuss how this could affect the way they adjust the dials so they can quickly and accurately represent the target number with as few adjustments as possible. To find 8.75 as quickly as possible, the user could adjust the Ones dial to the 8.5 range on the Ruler and then use the Hundredths dial to fine tune the number until they see the Ruler line up with 8.75.
 
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