## WeBWorK Main Forum

### Displaying answers with two decimals, but keeping student answers as is

by Rick Lynch -
Number of replies: 4

I am attempting to write some finance problems and I want the answers to display to two decimal places since they're supposed to represent money. I also want this to happen even when there are trailing zeros (like 21.10). I know I can use

Context()->{format}{number} = "%.2f";

to set the default format. However, the problem is that it also rounds the student answers, which is pretty undesirable as I am sure students will complain if their answer shows as rounded to the correct number, but they're not credit. An example of what I mean is pictured below in which I want the student's answer to show as inputted, 33.93115, but want the correct answer always displayed to two decimal places, including any trailing zeros if it were a different answer such as 21.10. I should note that I'm avoiding the special currency context since we don't want to make students enter the dollar sign.

### Re: Displaying answers with two decimals, but keeping student answers as is

by Alex Jordan -

Have you seen the Currency context? I think it might be a good fit for the problem you are writing. I recommend reading through the documentation so you know all its configuration options.

https://github.com/openwebwork/pg/blob/master/macros/contextCurrency.pl

### Re: Displaying answers with two decimals, but keeping student answers as is

by Rick Lynch -
Thanks, Alex!! Yes, I've used the Currency context before, but I wasn't aware there was a way to remove the need to enter a dollar sign, so this will certainly work for problems where monetary values are the answers. It also has the benefit that the correct answers now show up with the dollar sign. Great!

Now the issue is that I also want to do this for other problems that involve non-monetary numbers rounded to 4 decimal places. For example, the answer might be 6.5, in which case I want the answer displayed in the "Correct Answer" column to be 6.5000, and for students to enter any number of decimals and not have it automatically rounded in the "Answer" column, so 6.5111235 wouldn't show as 6.5111 and as inputted.

To be fair, none of this is really a huge deal, but I'm just patching up the edges so to speak from my instructors' requests. Again, thanks for your input!

### Re: Displaying answers with two decimals, but keeping student answers as is

by Davide Cervone -

One option is to set the number format before creating your answers via Compute(), and then set it back to the default afterward. Since the correct answer is set up by Compute() at the time it is run, they will have the precision in the number format that you set initially, and then when you set it back, that is what will be used for students.

E.g.,

Context()->{format}{number} = "%.2f";
$answer = Compute(21.1); Context()->{format}{number} = "%g"; BEGIN_PGML 211.00 / 100.00 = [________]{$answer}
END_PGML


Will show the student's answers with 6 significant digits, but will give the correct answer as "21.10".

In a situation where you are working with a small numbers of digits, you might want to be sure that your correct answer actually is the same precision as the displayed answer. For example, if you do

Context()->{format}{number} = "%.2f";
$answer = Compute(3.10455); Context()->{format}{number} = "%g";  then the correct answer will show as "3.10", but that will not be accepted as a correct answer with the default tolerances. Even with a relative tolerance of .001 (indicating roughly 3 digits of accuracy), this will still be marked incorrect. So you might want to do something like Context()->{format}{number} = "%.2f";$answer = Compute(prfmt(3.10455, "%.2f"));
Context()->{format}{number} = "%g";


so that the correct answer will be 3.1 not 3.10455 (due to the prfmt()), and still be displayed as 3.10 (due to the number format in the context). When you are showing 6 digits, but only requiring 4 (as with the default tolerances and formats), this is not an issue, but if you are showing exactly the number you are looking for, these problems do occur.