it does not work....
i tried over this question after going through your free video lecture and marked my right logically solved ques to wrong :P.
MathRevolution wrote:
Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.
In the number 1.4ab5, a and b represent single positive digits. If x = 1.4ab5, what is the value of 10 – x?
(1) If x is rounded to the nearest hundredth, then 10 – x = 8.56.
(2) If x is rounded to the nearest thousandth, then 10 – x = 8.564.
In the original condition there are 3 variables (x,a,b) and one equation (x=1.4ab5); 2 more equations are given from the conditions, so there is high chance (C) will be our answer.
If we look at the conditions together,
BY 1) 10-1.4ab5=8.56, BY 2) 10-1.4ab5=8.564, we get a=3, b=6, and the answer becomes (C). But this is a commonly made mistake;
if we look at them separately,
for condition 1, it is insufficient as x=1.4365, 1.4375
for condition 2, x=1.4365. This is sufficient, and the answer becomes (B).
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.