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Forget conventional ways of solving math questions. For DS problems, the VA (Variable Approach) method is the quickest and easiest way to find the answer without actually solving the problem. Remember that equal numbers of variables and independent equations ensure a solution.
When we apply the VA (Variable Approach) method to a triangle, we have 3 variables corresponding to the side-lengths of the triangle. Since each condition provides only one equation, E is most likely to be the answer. So, we should consider conditions 1) & 2) together first. After comparing the number of variables and the number of equations, we can save time by considering conditions 1) & 2) together first.
Conditions 1) & 2):
If the triangle is a right-angled isosceles triangle with two legs of length 10, then its area is (1/2)10*10 = 50.
If the triangle is an equilateral triangle with all sides of length 10, then its area is (√3/4)10^2 = 25√3.
Since we don't have a unique solution, both conditions are not sufficient, when taken together.
Therefore, E is the answer.
Answer: E
In cases where 3 or more additional equations are required, such as for original conditions with "3 variables", or "4 variables and 1 equation", or "5 variables and 2 equations", conditions 1) and 2) usually supply only one additional equation. Therefore, there is an 80% chance that E is the answer, a 15% chance that C is the answer, and a 5% chance that the answer is A, B or D. Since E (i.e. conditions 1) & 2) are NOT sufficient, when taken together) is most likely to be the answer, it is generally most efficient to begin by checking the sufficiency of conditions 1) and 2), when taken together. Obviously, there may be occasions on which the answer is A, B, C or D.
