6. Mode Settings
Mode settings offer another opportunity to take advantage of the 8-line screen capacity. Possible topics that lend themselves to a guided discovery lesson include:
- Scientific and Standard Notation
- Rounding Decimals
- Simplfying Fractions
The first two topics can be addressed using either a TI-8X or TI-73. However, simplifying fractions lesson applies to the TI-73 only.
Press your calculator’s MODE key to access these mode setting options. Note that the far left settings are the calculator’s default mode settings.
Scientific and Standard Notation
Normal mode means that most answers will be displayed in standard form. (Exceptions occur for numbers of very small or very large magnitudes, which are automatically expressed in scientific notation.) Sci (Scientific) mode means that an answer will be displayed in scientic notation.
The calculator uses “E” to indicate “10 raised to the __ power”. For example, an answer of 2.5E1 represents 2.5 times 10 raised the first power. This will need to be explained to the students at some time in the lesson.
Start your lesson by selecting the Sci mode on your overhead calculator. This is done by pressing the (blue)right arrow once and pressing ENTER.
Return to your Home Screen. Enter a number such as 25 and press ENTER. Repeat with other two-digit numbers until students see the pattern.
Repeat the process with three-digit numbers, four-digit numbers, etc. Have students predict the resulting answers.
Next, change the mode setting to Normal and return to the Home Screen. Enter expressions in scientific notation form, such as 2.5 * 10^2. Have students predict resulting answers.
If appropriate, repeat with numbers less than 0 and scientific notation expressions involving negative exponents.
To close the lesson, have students explain and/or write the procedure for changing from one form to another.
Rounding Decimals
The Float setting will automatically place the decimal point where it naturally occurs in any answer displayed in standard form. The number settings (0, 1,2,…) to the right of Float determine the number of decimal places to which a displayed answer will be rounded. For example, a mode setting of 2 will round an answer/entry of 0.043 to 0.04.
To introduce/reinforce the concept of rounding decimals, select the 0 mode setting on your overhead calculator and return to the Home Screen. Enter numbers, such as 20.1, 20.2, 20.3, 20.4, 20.5, 20.6, 20.7, 20.8, and 20.9. Record resulting outputs. Encourage students to make predictions based on previous outcomes. Repeat with other numbers to tenths until students have mastered the skill.
Repeat with a mode setting of 1 and numbers to hundredths, such as 45.11, 45.12, …
Repeat with a mode setting of 2 and numbers to thousandths, such as 45.11, 45.12, …
Conclude the lesson by having students provide a general rule for rounding and testing their rule with mode settings and examples provided by the students.
Simplifying Fractions
The TI-73 has mode settings that deal specifically with mixed number/improper fractions and auto/manual simplification of fractions. The Mansimp mode can be used to introduce/reinforce the simplification of fractions.
Select Mansimp on your overhead calculator and return to the Home Screen. Enter a fraction that is not in simplest form, such as 18/24. (To enter 18/24: enter 18, press the b/c key, enter 24, press the right arrow.)
Press ENTER. Ask students what the output is indicating. Once students realize that the calculator is indicating that 18/24 can be simplified, ask students for a factor. (It will not matter if students do not give the greatest common factor.)
Re-enter 18/24, press SIMP, enter the number supplied by the students, press ENTER. The calculator will display the fraction resulting from the supplied number being divided into both the original numerator and denominator. Three possibilities can occur:
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If the number supplied by the students was the greatest common factor, the resulting fraction is in simplest form and the answer does not include a down arrow.
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If the number supplied by the students was not the greatest common factor, the resulting fraction will not be in lowest terms and will need to be simplified further, as indicated by the down arrow.
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If the number supplied by the students was not a common factor, the original fraction will be displayed and a common factor still needs to be found.
Repeat with other fractions. Have students describe the process for simplifying fractions.
Parting Thoughts
If you give these a try, let me know how it goes.
Any tweaking?
Any other ides for utilizing mode settings?
