wonuorah wrote:Please how did we arrive at the answer E
I added the two statements and had x + 2y < 40. So what should we do next to conclude that E is the answer. Thanks
be very careful when you do this sort of thing -- if you combine TWO equations into ONE equation, the resulting equation does not carry as much information as did the two original equations.
in other words, it's quite possible to add the inequalities together and arrive at one, combined inequality that is NOT sufficient to address the given question -- even though the two inequalities, taken together, ARE sufficient to address the given question.
for instance, consider the following problem (from GMAT PREP)
Is m + z > 0?
(1) z - 3m > 0
(2) 4m - z > 0
if you add these two inequalities together, you get m > 0, which by itself
is not sufficient to address the question.
however, if you realize that the two original inequalities are still valid, then the observation that z > 3m (from statement 1), COMBINED with the combined inequality m > 0, lets you conclude that z is also positive -- which means m + z > 0. sufficient.
so, big takeaway here:if you combine two or more equations/inequalities in a data sufficiency problem, DO NOT FORGET ABOUT THE ORIGINAL EQUATIONS/INEQUALITIES.