HP Prime - Fraction/Decimal bug?

[Joshua09]

I purchased my HP Prime calculator about a month ago, and its been pretty awesome for the most part. I've noticed a problem the last week with trying to get a decimal form of a fraction like 1/101, where the answer it is giving me is 9.90099009901E-3.  On a standard sientific calculator I would get the correct decimal: 0.00990099009901, which tells me the decimal is off by three digits. I tried both CAS/nonCAS enviroments, and its giving the same answer. Is there anything I can do on my Prime to correct this issue, or a work-around?

Thank you,

Joshua

[Maké]

Hi!, Joshua09:

Change, in Home Seettings, to Fixed 11 ...

 

[Tim_Wessman · Accepted solution]

Hello,

The decimal is not off here at all. The E-3 part at the end means that it is reporting your 12 digit result with a x10^-3 power.

1E3 is the same as 1000. 1E-3 means .001. Not how in the positive E3, it shifted the value up 3 10s places. The  E-3 shifts it down 3 10s places.

In "standard" mode, rather then display .00990099009901, it removes the first few zeros and adds the exponent part. Why would it do this? Well, imagine if you have the number 6.022E23, or 6.022x10^23 (this is a very famous number used in chemistry in nearly every calculation!). It would be really tedious, and likely to cause errors, to write that out as 602200000000000000000000 - wouldn't it?

It is very common to write numbers in this way as it actually makes it easier to compare, write and understand them. What do I mean? Try this - which of these numbers is the smallest: 0.0000009347374, 0.00000543422 or 0.000003542? Did you have to count zeros?

What about now? 9.347374E-7, 5.43422E-6 or 3.542E-6

Yup, the first one is the smallest! At a glance you can see which is the smaller number. (see https://www.mathsisfun.com/numbers/scientific-notation.html if you'd like to learn a bit more)

However, if you really don't like this, you can set your display to be the "rounded" form. Go to your home settings ( [SHIFT] [HOME] ) and change the "Standard" to be "Rounded". This will adjust your numbers so something like .000012345678 will show as .00001235 instead if you prefer that type of display.

You will still want to learn what the E<number> form of a number means though, because even in rounded form it will need to display results in scientific notation once the number gets sufficiently large or small that it no longer fits!

[Joshua09]

Thanks for the help Make, and Tim. After reading your detailed explanation I'll keep the calculators current setting.

[Maké]

Hi !, Joshua09:

For learn, the use, of HP PRIME, consult ...  www-fourier.ujf-grenoble.fr/~parisse/calc/hprime .pdf

[Maké]

Hi!, Joshua09:

You too, can select the Format Floating with 11 decimal's.