Conversion of decimals to fractions 0.1666666666666666666666666 = 1/6

Conversion is not always possible. If a decimal result has just been found and displayed, pressing the [a b/c] fraction button may convert the result still in answer memory (ans) to a fraction. But if you alter the value of answer memory and type in the (approximate) decimal value that you copied from the screen, you may not get your correct fraction.

The way it works is as follow. If a result is displayed as a fraction you can convert it to its decimal representation. If you do nothing after the conversion, you can revert the decimal representation to the fraction.

If you are concerned about fraction handling and conversion to decimal representation, upgrade the OS of your calculator to 2.5x MP. As to handling of irrational numbers (such as square roots) you should visit the TIcalc.org website to look for any 3rd-party program that can do that.

None of these solutions answer his question. When converting a fraction or any number with decimal places to Binary, the TI-89 gives "Error: Domain error." For example, entering .6875 [2ND][MATH][BASE][BIN] does not work. I haven't found a way to do it with built in functions. In order to do these types of conversions, I use the following method.

Convert: 0.6875 to Binary
- left of decimal is a 0, so write down a 0, then a decimal point: (0.)
- multiply .6875 x 2 = 1.375 left of decimal is 1, write a 1: (0.1)
- drop the 1 and multiply .375 x 2 = .75 left of decimal is 0. write a 0: (0.10)
- multiply .75 x 2 = 1.5 left of decimal is 1, write a 1: (0.101)

- drop the 1, multiple .5 x 2 = 1. left of decimal is 1, write a 1: (0.1011).
- since there is no more fraction, the final answer is (0.1011). Hope this helps.

The calculator has two Input/Output modes: MathIO and LineIO.

LineIO
LineIO is the old way of entering numbers in calculators and results are always displayed as decimal numbers. Some calculators have a fraction feature and would convert a fraction to a decimal number and back.

MathIO
In MathIO you enter expressions as you would by hand or as you see them written in textbooks.
In this mode, results are by default displayed as fraction or fractions/ radicals.
Conversion
To convert the fraction/radical to decimals you just press the [SD] key. If you press again you cycle through all the available display formats.
So you can (if you want) use the MathIO to manipulate expressions and convert only the last result to decimal. By the way, fractions and radicals are generally more accurate than their decimal representations.

SetUP
If however seeing fractions and radicals is too painful, just set the LineIO as your default mode. To do so press [SHIFT][MODE] to open (SETUP), then select [2:LineIO]

Enters a proper or improper fraction,
b?c (b { 6 digits, c { 3 digits). When
possible, improper fractions are
displayed as mixed numbers.
3 F 4 3?4
8 3 J 21?4
Single-variable functions display
decimal results.
1 F 2 0 0.25
a F b F c Enters the mixed fraction a b?c.
(a, b, c { 3 digits each, with the total
digits { 8).
6 F 4 F 6 64?6
J 62?3
"s Toggles display between a mixed
number and an improper fraction.
30 F 4 30?4
"s 71?2
"s 15?2
"s 71?2
"y Toggles display between fraction and
decimal.
55 F 24 55?24
"y 2.291666667
"y 27?24
If a result would overflow or if fixed decimal is 0, no
fraction to decimal conversion occurs. It is not an error.
Denominator must be a whole number {999.

There is no built-in conversion between decimal and fraction.

Pressing the [S

1. Put a decimal mark at the end of one integer in the expression, 15./2 or 15/2. or 15./2. all give 7.5 as result
   
2. OR press [diamond][ENTER] to force conversion of a fraction to a decimal number,
3. OR press [MODE][F2] and scroll to line EXACT/APPROX, press right arrow to unfold the menu list and select [3:Approximate]
   

Hello,
Once you enter a fraction the calculator calculates it and displays a decimal result.So basically you cannot do fraction manipulations. However you can convert a decimal result into a fraction. To do the conversion, you enter the decimal number then you Press [MATH] and [1]. ( -->Frac) The number will be converted.
Similarly you can enter a fraction to a decimal number (-->Dec)
[MATH] [2:] [ENTER]. But I see no point in doing that, because any fraction entered is displayed as a decimal number.

Hope it helps