The most frequently asked question by CET aspirants to any mentor is how to approach lengthy Logical Reasoning sets. To modify what Shakespeare wrote in the Hamlet: To solve, or not to solve, that is the question! I hope this post will offer some insights regarding the approach towards such lengthy logical reasoning puzzles.
The elements to look for while deciding whether to solve a set or not are:
The length and composition of the set: If the set is very lengthy with more than 10 bullet points or reads something like: 8 people sitting around a circular table facing towards and away from the centre coupled with blood relations, it’s a clear indication that it’s going to be time consuming. Whereas something which has fewer people involved with fewer attributes might be a better choice.
Familiarity of logic or structure: If you have seen a similar question earlier and have solved it, solving it during the test is going to be easier because you know the structure that you need to put in place in the beginning. For example, if it is floors numbered 1 to 8 with people staying on different floors and owning different brands of phone, you start by writing floors in the form of a column starting with 1 at the bottom and 8 at the top and then place people or phone brands.
Presence of direct or condition questions: If you quickly glance through the questions and see more questions starting with ‘IF’ or any other conditional word, you should understand that the data in the set is incomplete and you will have to write cases for each conditional question to reach the answer. The hallmark of a doable set is presence of more direct questions or absence of ‘can not be determined’ option.
The decision of whether to solve or not should not take more than 30 seconds. Once you overcome this challenge, the next part is putting in the data.
Some useful tips
- Negations should be written outside the table and not inside the table (for grouping, team formation, arrangement, assignment-based questions)
- Put the definite information first before you go to cases. If there are 10 bullet points through which the data is presented, you might have to jump a lot but take care of one condition at a time starting with the definite ones.
- Be extremely systematic so that you don’t mess things up. Case writing is an art. Don’t make random assumptions while writing cases.
Let’s look at a set that appeared in one of the SimCETs:
Approach: When we look at this set, we see that we have to place 10 people on 12 seats. Though some of them are facing south and some of them are facing north, we know who these people are. A cursory glance tells us that the maximum information is provided about person number 4 so that’s where we can possibly start. Something that can help is writing down condition numbers and striking them out as you progress through the set.
As you go through conditions 5, 7, and 10, we see that there are broadly three possibilities with respect to F and G, but two of them are invalid and can be eliminated. We now need to work on the middle case that I’ve written below and start placing elements that can be placed definitely.
Adding the next set of conditions, we get: 3 and 8 are opposite to each other and 1 and 8 are adjacent. F is neither 1 nor 8 and P sits opposite F. Number 9 is opposite number 4 or G.
Having reached this stage, we will now consider condition 1, 6, and 14 to position N and O. Though there are four possibilities given the spacing between N and O, the first two are invalid as they’re not facing North. The third is invalid as it will increase the number of seats in the first row. So, we are left with only one case which is N _ _ O and with O at one of the extremes, we get definite positions of N and O.
The catch in this question is condition no. 13 where the absence of word ‘immediate left‘ makes it difficult and that’s why I considered all other conditions first before putting in that condition. If we had started with that, at some point, we would have reached some or the other contradiction. Once we take care of all the remaining conditions, we get definite positions of D and H are the corners and the vacant spaces as well as they’re neither opposite to each other nor at the extremes.
And finally, we’re left with numbering the people that we’ve placed. As 8 and 1 are adjacent, they clearly can’t be in Row number 2 and have to be in Row number 1. D can’t be 8 as H is 5. Hence, D is 1, P is 8 and F is 3. Placing the remaining people in each of the rows, we get final arrangement with only two people without definite numbers as:
The rough work required to get to the answers of this set shouldn’t exceed beyond this last image. Also, I’ve written a few extra things from an explanation perspective and need not be explicitly written while solving.
It’s impossible to take each and every set out there and explain the approach. But what’s really important is the thought process. Even if you practice all the sets from proctored and take-home SimCETs, I think you should be in a fair position to handle lengthy LR sets. What will ultimately make the difference is your thought process, meticulousness and speed of implementation.
Hope these posts are helping you. Please get in touch if you need any help. If there are any queries, please leave them in the comments below and allow me a few days to get back. Share this with your friends and co-aspirants. Happy prepping! 🙂