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I was doing some simple maths for a project when I stumbled upon an error (?) in my calculator (casio fx 991), I'll explain:

I wanted to make the next rule of three calculation:

$$ \frac{x}{4}=\frac{0.74}{1.7} \longrightarrow x=\frac{0.74 \cdot 4}{1.7} $$

by putting $0.74 \cdot 4$ on the calculator, it equals to $2.96$, by now it is correct.

then, I press $\texttt{Ans} \div 1.7$ and it gives me $1.024...$ as result.

when putting this result back on the first equation, something doesn't feels right.

$$ \frac{1.024}{4}=\frac{0.74}{1.7} $$

then, I used the Symbolab website to make sure it was right, and it was wrong, I found out $x$ should be equal to $1.74$.

what is the problem here? is it something about how calculators work? i am sure i didn't commited a mistake.

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  • $\begingroup$ There is something wrong here ' i press Ans÷1.7 and it gives me 1.024... as result' $\endgroup$
    – Shailesh
    Jun 2, 2021 at 23:36
  • $\begingroup$ Clearly, $\frac {2.96}{1.7}\neq 1.024$ $\endgroup$
    – lulu
    Jun 2, 2021 at 23:37
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    $\begingroup$ You somehow divided twice 2.96 / 1.7 / 1.7 ≈ 1.024. $\endgroup$
    – dxiv
    Jun 2, 2021 at 23:38
  • $\begingroup$ Seems there's another previous calculus whose result is 1.74, so Ans used it $\endgroup$
    – Ripi2
    Jun 2, 2021 at 23:38

2 Answers 2

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Each of the steps you did was correct, until you divided by $1.7$. If you divide by $2.96$ by $1.7$ once, you get $1.74$ as expected. The problem was you divided by $1.7$ twice (as dxiv mentioned in the comments above), giving you $1.024$.

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  • $\begingroup$ now i see it, it was because it gave a fracctional answer first and i wanted it in decimals, i pressed shift+= and it counted with the last answer. Thank you and dxiv. $\endgroup$
    – Francisco Arellano
    Jun 2, 2021 at 23:56
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I think you may have pressed = twice in a row

Mine hidden in a cupboard takes 0.74 × 4 = and gives $\frac{74}{25}$ which is indeed $2.96$. (How do you turn fractions off?)

Then doing Ans ÷ 1.7 = gives $\frac{148}{85}$ which is $1.741176471$

But pressing = again gives $\frac{296}{289}$ which is $1.024221453$ as it repeats the division by $1.7$.

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