#12 - Editorialist: Drivers with a large number of demerit

[Poonam Agrawal]

Hi Mahmed!

Thanks for your question - this one is definitely a tricky one to diagram. Here's how I would proceed, given the way you have started the diagram:

DP = Large number of demerit points
CS = Convicted of a serious driving related offense
J = Jail
R = Reeducation
LBR = Likely to become a responsible driver (added this one to your original key)

Sentence 1: DP & CS J or R
Sentence 2: R LBR (the "only if" creates this relationship)
Sentence 3: DP LBR

Then, consider the contrapositive of sentence 2:

LBR R

Which leads us to the following relationships:

DP LBR R
DP & SO J (is the only option left)

So, back to your original question - you don't necessarily need to look at the contrapositive of the first sentence. It is more helpful to consider all three sentences and figure out which contrapositives (in our case, the one from sentence 2) will lead you to a correct answer choice.

Hope that helps! Let me know if there's any part in the diagramming that is unclear.

[jmulder615]

It's crazy how this entire question hinges on the reader recognizing that it says "such drivers", which refers to the entire group, instead of saying it should be addressed case-by-case. The entire group is almost never going to be made more responsible which essentially disqualifies the possibility of re-education.

[Luke Haqq]

Hi jmulder615!

You're right to be on guard for words like "such drivers." Similarly, it's important to be aware of demonstratives like "these" and "those." If there's any confusion, it can be helpful to circle a word like that and draw it back to whatever subject is being referenced from a previous sentence or clause.

The stimulus in this question is saying that one of two options should occur--either re-education or jail time. The stimulus then concludes that re-education is not a viable option (it should only be an option if it makes "such drivers" more responsible, but it won't make them more responsible). This leaves jail as the remaining option.

[soyzoy]

Hello,

I'm wondering if this problem can still be solved if the diagramming of the start of the stimulus looks like:

J DE
DE J

This is what I did, but I'm having a hard time getting to the right conclusion using this form of either/or diagramming (negating the necessary conditions instead of the sufficient conditions).

Thanks!

[Jeff Wren]

Hi soyzoy,

Unfortunately, what you've diagrammed is not correct.

Your diagram represents a "not both" statement rather than an "either/or" statement, which is what is used in the stimulus.

Your diagram basically shows "if jail, then not driver education" and the contrapositive shows "if driver education, then not jail." This conditional leaves open the possibility of just jail, just driver education, or neither.

This is not equivalent to an either/or statement, which states that if one thing does not happen, then the other must happen. In other words, "either/or" means "at least one" of the things must happen, possibly both.

In short, the negative sign goes on the sufficient condition for "either/or" statements and on the necessary condition for "not both" statements. This distinction used to be tested quite often in logic games, but it is still important in certain logical reasoning questions with conditional reasoning.

For more information on conditional reasoning, including how to diagram "either/or" and "not both" statements, check out chapter six of "The Logical Reasoning Bible."