We have already discussed the basic of syllogisms in our previous notes. Today, we will discuss reverse syllogism as many of you are curious about this topic.
Reverse Syllogism is nothing but another version of syllogism in which Conclusions are given and you have to find out Which statements follow these conclusions.
Many aspirants are panicked due to this new type of Syllogism. We suggest you not to panic but focus on its basics. Once you understand it, we ensure you, you will be able to solve it within 40 -50 seconds. We recommend you to first learn basics of this topic and it will help you in the exam.
How to approach Reverse Syllogisms in the exam?
Preferable method to solve Reverse Syllogisms is Elimination method. In this method, we try to eliminate the options step by a step which cannot be answered. Steps should be taken in eliminating the options are given below.
- First, always identify “Universal Negative” conclusion, then eliminate those options which do not have a single universal negative statement.
- Secondly, check “Particular Negative” conclusion, then eliminate those options which violate this condition.
- Thirdly, check “Universal Positive” conclusion, then eliminate the option which also violates this condition.
- In last, check “Particular positive” conclusion, then eliminate the option which also violates this condition.
- In last the remaining option will be your answer.
Let's discuss it with examples
Example 1
Conclusion:
(1) No toxic is injection. (2) Some injections are glucose.
Statements:
(A) All toxic are tablet. No tablet is glucose. Some glucose are medicine. All medicine are injection.
(B) Some toxic are tablet. All tablet are injection. Some injection are glucose. All glucose are medicine.
(C) All tablet are toxic. No injection is toxic. Some glucose are injection. All glucose are medicine.
(D) Some injection are toxic. All injection are tablet. Some toxic are glucose. All glucose are medicine.
(E) Some medicine are toxic. Some toxic are injection. Some injection are tablet. All tablet are glucose.
Solution:
In Reverse Syllogism, Conc.1 is Universal negative or disjointed set. So first we will try to find out the option which has the statement following this conclusion.
We can see that, In option B, D and E, there is no negative statement. So these cannot be answered.
In option A and C, there is a negative statement. In option C, you can see the statement 2 and statement 3 depict the given conclusion. So, C is the answer.
You can also check option A, but when you have got your answer, there is no use of wasting time.
Now, Question is why I checked first option C?
I checked both option A and C, but in C I found related information to Conclusion, So, I go into detail of it.
Example 2
Conclusion:
(1) No toxic is injection. (2) Some injection are not glucose.
Statements:
(a) All toxic are syrup. Some syrup are glucose. Some glucose are medicine. All medicine are injection.
(b) Some toxic are syrup. All syrup are injection. Some injection are glucose. All glucose are medicine.
(c) All syrup are toxic. Some toxic are not injection. Some glucose are injection. All glucose are medicine.
(d) Some injection are not toxic. Some injection are not syrup. Some toxic are glucose. All glucose are medicine.
(e) No medicine is syrup. All toxic are medicine. All injection are syrup. No syrup is glucose.
Solution:
In this also conclusions are “No toxic is injection” and “Some injection are not glucose”.
First, we will identify the option which has statements depicting “No toxic is injection”.
Except option E, all options do not have any “Universal negative” statement. So our answer will be E.
If your basics are clear, no need to check the option E. Still for your convenience let’s check Option E.
We can see that All toxics are medicine, All injections are syrup and no medicine is syrup. So, no toxic is injection.
All injections are syrup and No syrup is glucose. So, no injection is glucose which infers that some injection is not glucose.
Example 3
Conclusion:
(1) All toxic are injection. (2) Some glucose are not medicine.
Statements:
(A) All toxic are syrup. Some syrup are glucose. Some glucose are injection. All medicine are injection.
(B) All toxic are syrup. All syrup are glucose. Some toxic are not medicine. All glucose are injection.
(C) All syrup are toxic. Some toxic are injection. Some glucose are injection. All glucose are medicine.
(D) Some injection are not toxic. No injection are syrup. No toxic are glucose. All glucose are medicine.
(E) No toxic is syrup. All syrup are glucose. All toxic are medicine. All toxic are injection
Solution: In this, there is no universal negative statement. Now, we will first focus on the Particular Negative statement.
In option A and option C, there is no negative statement, so these options are eliminated.
In option D, the last statement is “All glucose are medicine” given, so it will not be the answer.
Now let’s check option E and B.
In option E, the last statement has already depicted the first conclusion, but there is no restriction on Glucose and medicine. So, this will also not be our answer.
We have already eliminated four options. So the remaining will be our answer i.e. B.
Now let’s check option B. But, in exams you don’t need to check when you have elimated four options.
We know “some toxic are not medicine” means atleast one element of toxic is not medicine.
In diagram B.1, all toxic are glucose so, so at least one element of glucose will not be medicine.
Example 4
Conclusion:
(1) Some car are bus. (2) No bus is plane. (3) All plane are train
Statement:
(A) Some car are not plane. All drum are train. Some bus are not plane. All planes are drums.
(B) Some bus are car. All bus are train. No plane is bus. All car are train.
(C) Some bus are car. Some car are plane. Some train are plane. No plane is bus.
(D) All bus are train. All plane are drum. Some bus are car. All drum are bus.
(E) All drum are train. No train is car. All bus are car. All plane are drum.
Solution:
In given conclusions, Conc.2 is universal negative type. So, we will first identify options which have this type of statement.
Option B, C and E are this type of statement, so options A and D are eliminated.
In option B and C, statement “No plane is bus” available. Let’s first see these both option.
In option B, there is no relation between plane and train. This option is also eliminated.
In option C, If we check Conc.3 “All plane are train” which is universal affirmative for it statements should be also universal affirmative. So, this option is also eliminated.
So, answer is E. Let’s check it also.
Syllogism Concept Part 1 Notes
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