Standard aluminum soft-drink cans do not vary in the amount of aluminum that they contain. Fifty percent of the alumi...

Naz on October 15, 2015

You can access the video explanation by tapping the play button on the screen.

Hope that helps! Please let us know if you have any other questions.

marissaflores on October 21, 2019

The explanation video still does not make sense to me, I don't understand how C is the correct answer.

shunhe on December 20, 2019

Hi Jojo,

Let's say there are 20 cans in Group M, each with one unit of aluminum, leaving 20 units of aluminum. Since the aluminum came from group L, that means group L had 10 units of aluminum. We then conclude from this that group M has twice as many cans as group L. Note that one assumption here is that the cans require the same amount of aluminum, but this isn't one of the answer choices; we can safely assume that L had 10 cans. First, note that (A), (B), (D), and (E) seem irrelevant. The recyclability of the cans in group M has nothing to do with the ideas presented, as well as how easy aluminum is to recycle vs. other materials, if the cans in group L were recycled or not, and the relative quality of recycled materials.

We now turn to (C). Let's assume the (C) is false and that not all of the aluminum can be recovered; let's say that only half the aluminum can be recovered from a recycled can. That means that in order to produce 10 units of aluminum, group L would have had to have 20 cans. But then group L and group M would have had the same number of cans, a contradiction. So (C) is an assumption integral to the process. Hope that helps! Feel free to ask any other questions.