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I have a CASIO fx-350MS, and I need to make fraction computations, like $\frac{7}{2} \cdot \frac{4}{5}$ for an exam where I have to compute a lot matrix multiplications (programmable calculators aren't allowed). If I compute something like $\frac{7}{2} \cdot \frac{4}{5}$ I get 2.8 as result, which can be converted to a fraction pressing shift and "a b/c".

The problem is that often I don't get precise values, specially when I make a lot of counts, and I need precise values. So the question is: is there a way to store two integers for every fraction, so that the error is zero, instead of using floating point numbers? If not, is there another calculator able to do that?

miracle173
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Ramy Al Zuhouri
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  • Please change the label. This is not about fractional calculus. Also, there are some Sharp calculators which give answers in exact form. – Pratyush Sarkar Sep 06 '13 at 18:25
  • Yes, there is a way to store the two numbers. This is given by the definition of the arithmetic operations on fractions. For example: $\frac{a}{b}\cdot\frac{c}{d}$ is defined to be $\frac{a\cdot c}{b\cdot d}$. So you just compute $ab$ and $b\cdot d$ and store those two values. – OR. Sep 06 '13 at 18:34
  • Likewise for addition: $\frac{a}{b}+\frac{c}{d}$ is defined to be $\frac{a\cdot d+c\cdot b}{b\cdot d}$. So, compute $a\cdot d+c\cdot b$ and $b\cdot d$ and store those two numbers. – OR. Sep 06 '13 at 18:35
  • Could you give us a better idea of an example problem? About how long is a typical string of computations using fractions that you face? – rschwieb Sep 06 '13 at 18:47
  • $2.8$ can also be converted into a fraction by just looking at it and writing $28/10$. :) ...but you are probably thinking of more complex decimals when you are asking this question. – rschwieb Sep 06 '13 at 18:48

1 Answers1

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CASIO fx-350MS is able handle fractions. This is described in the manual at page E-11. I suppose you press the wrong keys. To calculate $\frac{7}{2} \cdot \frac{4}{5}$ you should enter the following keys

7
a b/c
2
*
4
a b/c
5
=

The result should be

14_5

If the result cannot be displayed because ist needs too many characters it is displayed in decimal notation.

You should not enter

7
:
2
*
4
:
5
=
miracle173
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