Numeric values with units of measurement (Simple Editor)

When evaluating the equivalence of a student submission to the correct and incorrect answers you code, the Mastering answer engine uses the following guidelines:

• The units students enter are compared to the units you code before the numeric values are compared. If the units are not equivalent, no comparison of the numeric values are made.

• The equivalence of the numeric portion of any two physical quantities follows the same rules as for answers in the numeric value or expression answer type. That is, incorrect items that evaluate as equal (within tolerance) to a specific pre-defined value according to the algorithm used in the answer engine, are considered equivalent. However, there is one exception: Students can't enter mathematical expressions into the numeric value with units answer type. For example, students can't enter 12+12 in this answer type, even though that entry is acceptable for numeric value or expression answers.

Note: For a correct answer, students can’t enter an expression to be evaluated in place of a numeric value. In other words, they can’t use the form 2 + 2, tan^-1(1), e^x, and so on.

• Combinations of base units: In most cases, students can enter combinations of base units even when there is a standard unit monomial. For example, a student can enter “kg*m/s^2” in place of “N” for SI units of force.
• Supported SI prefixes: SI prefixes are recognized only on those units explicitly identified in the list of supported prefixes and units.
• Supported compound units: Compound units are supported only as identifed in the list ofsupported prefixes and units, regardless of whether the constituent base units are supported.
• Zero numeric value: When both your answer and the student entry have a numeric value that is zero, they are equivalent even if one has a unit and the other does not.
• Two physical quantities expressed in different unit systems: These are NEVER equivalent.
• Two unit monomials: These are equivalent only if they are identical, including case (J and j are not the same).
• Two physical quantities expressed in different units: These are equivalent if their numerical value is equal (within tolerance) after converting both to the same unit. For example, “1 ft” and “12 in” are equivalent. Compound units are converted as a whole; base units are not individually converted.
• Temperature units: These are NOT equivalent. If an answer is either degrees Celsius or kelvin, you should code an alternate correct answer in kelvin or degrees Celsius. The conversion between temperature scales is prohibited because a temperature reading of 10 K converts to Celsius differently than a temperature change of 10 K.

To determine whether two compound units are equivalent:

• They must involve identical base units. The following are not equivalent:
  

• They must be mathematically equivalent, treating each base unit as a variable. The following are all equivalent:

• Base units can be in any order. The following are equivalent:

• Base units must be to the same power. The following are not equivalent.

• They are acknowledged to measure the same physical quantity and reduce to the same combination of base units. For example, electric potential (V), can be reported in units of J/C and W/A. The list of supported prefixes and units contains compound units considered equivalent for various physical quantities.
• Multiplication must be explicit, either via multiplication symbols or templates. The following are not equivalent:

• Both cdot and dash are acceptable multiplication symbols for compound units. The following are equivalent:

Note: You must use * for multiplication in compound units when you code correct and incorrect answers.

Check the box for "Exact unit match" when you want students to explicitly match the unit answer you provide.

• Click the add solve for link to enter text or a mathematical expression that will appear before "=", such as "m , x". The equals sign is supplied for the answer—you don't have to enter it.
• Click the add pre-text link to enter text to appear before the answer.
• Click the add post-text link to enter text to appear after the answer.

For numeric answers, student answers are considered correct if they match the coded answer to the specified grading tolerance. In general, you can accept the default tolerance value of 2%.

• [Optional] To change the grading tolerance: Specify another value in the box for Acceptable variation or rounding error.For more information on grading tolerance, see Significant figures and tolerance.
  

• [Optional] To show the rounding message to students: Click the check box for Show additional rounding message... when the student response from the current part is used for a calculation of a subsequent part. For example, the student calculates a response for Part A. The response from part A is needed in the calculation of Part B. The student should use the full precision number from Part A in the Part B calculation.

  The additional rounding messages that displays to students is:
  "If you need this result for any later calculation in this item, keep all the digits and round as the final step before submitting your answer."

  For more details, see How significant figures and tolerance work in Mastering and/or Guidelines for setting significant figures and tolerance.

1. Under Correct Answer, enter the correct answers in the Number (that is, a numeric value) and Units boxes.

   • Numeric value answer: Enter a numeric value or expression.

     MasteringPhysics and MasteringEngineering vector notation

     You must code vector answer values using infix, with subscripts using tags that end in either vec or evec. For physics: F_k_vec is the only acceptable notation for vectors with subscript answer values. For engineering: F_k_evec is the only acceptable notation for vectors with subscript answer values.

   • Units answer: You can enter supported TeX code for this answer type directly into the units text box for the correct answer. Use * for multiplication in compound units.
     
     About supported TeX: Supported TeX renders in the text box. If the TeX does NOT render, the answer is not supported. The Greek letter TeX codes supported for this answer type are \mu and \Omega.
     
     For additional guidelines on units, see the section above, "About numeric equivalence for numeric with units answers" or click the accepted units link for information about units, prefixes, and how to enter the units that Mastering recognizes.
     
     

2. [Optional] Answer format (display of significant figures): Numeric answers are displayed to 3 significant figures, without using scientific notation for values like 200. Mastering evaluates the student answer against the truncated formatted correct answer. When this box is blank, the default value of 3 significant figures is in effect; only enter a value if you want to change the default value. More information about significant figures

   If you do reset the number of significant figures required for the correct answer, you should specify the new value for students in the instruction text. (This is the only way students will know that the usual default precision does not apply.)

3. [Optional] Add an alternate correct answer: Click the add an additional correct answer link and add another set of Number and Units answers.

   About degrees Celsius and degrees kelvin units: The units of degrees Celsius and kelvin are NOT considered equivalent units when matching students’ answers. If you want both units to be accepted, add correct answers for both units. For an exact match, you just need to provide one answer, since the system accepts only the unit (Celsius or kelvin) you specify.

   About ampere units: In MasteringChemistry, answers in amperes must be coded in both A and amp. Use A for the first answer listed. However, for MasteringPhysics and MasteringEngineering, amp is not considered correct—use only A for these disciplines.