Calculator usage: fraction format on the Casio fx-991ES PLUS C

Tutoring math, one notices features of calculators. The tutor mentions a way to set the default format of fractions to improper on the Casio fx-991ES PLUS C.

The following is according to my understanding.

For background on mixed numerals and improper fractions, one might look to my post from October 21, 2013. The basic idea is that 21/5 is an improper fraction, while 4¹/₅ is the same value as a mixed numeral.

In everyday life, people tend to use mixed numerals more, such as 2¹/₂ cups of flour. Yet, in math past grade 9, improper fractions are used more: 5/2 cups of flour. The reason is that computations tend to be easier from the improper fraction form, especially mixed computations.

A fraction means the top divided by the bottom: 10/6 means “ten divided by 6.” On the Casio fx-991ES PLUS C, if one keys 10÷6, one might likely get the mixed numeral form, 1²/₃. Then, one can key Shift S<=>D (the S<=>D key is middle right, next to M+, on the model I’m using) to get 5/3, which is improper form. 10/6 = 5/3: the calculator has reduced it.

One might get tired of always having to convert the mixed numeral to the improper fraction. In such a case one can set the calculator so it defaults to improper fraction form. It’s in the SET UP menu. The key sequence is Shift, then Mode, then Down Arrow (bottom of the round key below the display), then 2.

Neat, eh?

Source:

casio.com: fx-991ES PLUS C User’s Guide