Once we modify the original condition and the question according to the variable approach method 1, we can solve approximately 30% of DS questions.
If n and k are positive integers, is n divisible by 6?
(1) n = k(k + 1)(k - 1)
(2) k – 1 is a multiple of 3
This is a recently common type of question.
There are 2 variables (n,k) and 2 equations are given from the 2 conditions, so there is high chance (C) will be our answer. Looking at the conditions individually,
for condition 1, n becomes a product of 3 consecutive integers, so this always makes it a multiple of 6, so this is sufficient.
for condition 2, there is not information about n, so this is insufficient, and the answer becomes (A).
We cannot look at the conditions together as this is a commonly made mistake type 4(A).
For cases where we need 2 more equation, such as original conditions with “2 variables”, or “3 variables and 1 equation”, or “4 variables and 2 equations”, we have 1 equation each in both 1) and 2). Therefore, there is 70% chance that C is the answer, while E has 25% chance. These two are the majority. In case of common mistake type 3,4, the answer may be from A, B or D but there is only 5% chance. Since C is most likely to be the answer using 1) and 2) separately according to DS definition (It saves us time). Obviously there may be cases where the answer is A, B, D or E.
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