Compute operations with fractions using calculator

Question

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?

Answer 1

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
=