<p>Let me try to explain in a different way why I think this wording of this question is problematic.</p>
<p>First, note that the question itself involves an ellipsis of material after ‘need’, which can be filled in as follows (reconstituted elliptical material in brackets).</p>
<p>How long a piece of ribbon does he need [to wrap around a box measuring 3X8X12 cm]?</p>
<p>Here, the reconstituted element contains only material from one of the conjoined verb phrases. You would solve the problem for only the amount of ribbon around the box, which is 52cm, and give choice (b).</p>
<p>Now, it is possible to find situtations in which the reconstituted elliptical material <em>must</em> be only taken from one of the conjoined verb phrases. You need to have a biasing context here.</p>
<p>Biasing context: Stu has 16 students in his science class.</p>
<p>Stu wants to take as many students as he can to the local science musem and have 3 left behind to supervise the on-going experiments.</p>
<p>Question: How many students does he need?</p>
<p>Here, you would only look for the number of students he needs to take to the local science museum.</p>
<p>Now, the question given does not have the biasing context, but that doesn’t mean that a student might not provide a biasing context such as </p>
<p>Context: Stu has a certain length of ribbon.</p>
<p>Stu wants to wrap some ribbon around a box (etc. etc.) and have 25 cm left for the bow. How long a piece of ribbon does he need?</p>
<p>The student might interpret this as a question of ‘the (least) amount of ribbon needed to cover the box so that there is 25 cm left for the bow’–you don’t want to use up too much ribbon so that there isn’t enough left for the bow. So you solve for the least amount of ribbon to cover the box as shown.</p>
<p>Note that this isn’t that different from the above with the science class–the amount of students to take so that there are 3 students left to supervise the experiments.</p>
<p>I would also say that stating ‘having 25cm left’ might also cause trouble, because of the word ‘left’. The question wants the total amount of ribbon, including the amount ‘left’. But usually, the stuff that is ‘left’ is typically not part of a total.</p>
<p>Of course, if you do go this route, then you are in trouble. Because then you have to battle trying to figure out the ideology of the test maker. If you go this route, you then wonder why 25 cm is given at all, since this number is not used in the calculation. You may try to say that this is ‘distractor information’–to be ignored. Or you may say that there are two unknowns–the original length of ribbon and the amount around the box and that the problem involves more complex math than you first realized or know how to do. </p>
<p>Or you can go and reread the question again, figure out that the question asks for both the amount for the box and the bow and get it right.</p>
<p>But here, you are battling not a bad math background but a problem of interpretation.</p>
<p>And, as I stated previously, perhaps the wording in other languages does not allow the student to go the route that I did, thus making the problem a bit easier.</p>
<p>So that is why I am curious if 52cm wasn’t the most likely ‘error’. And note that to get this 52cm, you do need to know the basic math involved.</p>
<p>So simply stating that only 32% got this right tells us nothing about why they got it wrong and little about what we need to do to correct the problem.</p>