AnswerWithUnits1
From WeBWorK
Answer is a Number or Formula with Units
This PG code shows how to require students to enter units with their answers.
 File location in OPL: FortLewis/Authoring/Templates/DiffCalc/AnswerWithUnits.pg
 PGML location in OPL: FortLewis/Authoring/Templates/DiffCalc/AnswerWithUnits1_PGML.pg
PG problem file  Explanation 

Problem tagging: 

DOCUMENT(); loadMacros( "PGstandard.pl", "MathObjects.pl", "parserNumberWithUnits.pl", "parserFormulaWithUnits.pl", ); TEXT(beginproblem()); 
Initialization:
We load 
Context("Numeric")>variables>are(t=>"Real"); $h = Formula("16 t^2 + 16"); $v = $h>D('t'); $v1 = $v>eval(t=>1); $a = $v>D('t'); $answer[0] = FormulaWithUnits("$v","ft/s"); $answer[1] = NumberWithUnits("$v1","ft/s"); $answer[2] = FormulaWithUnits("$a","ft/s^2"); 
Setup:
We use the differentiation operator 
Context()>texStrings; BEGIN_TEXT Suppose the height of a falling object, in feet above the ground, is given by \( h(t) = $h \) for \( t \geq 0 \), where time is measured in seconds. $BR $BR (a) What is the velocity of the object? Include units in your answer. $BR \{ ans_rule(20) \} \{ helpLink("units") \} $BR $BR (b) What is the velocity of the object when it hits the ground? Include units in your answer. $BR \{ ans_rule(20) \} \{ helpLink("units") \} $BR $BR (c) What is the acceleration of the object? Include units in your answer. $BR \{ ans_rule(20) \} \{ helpLink("units") \} END_TEXT Context()>normalStrings; 
Main Text:
Don't forget to use 
$showPartialCorrectAnswers = 1; foreach my $i (0..2) { ANS( $answer[$i]>cmp() ); } 
Answer Evaluation: 
Context()>texStrings; BEGIN_SOLUTION Solution explanation goes here. END_SOLUTION Context()>normalStrings; COMMENT('MathObject version.'); ENDDOCUMENT(); 
Solution: 