Don't
get carried away with solving a DS problem, all the times.
The main point here is, in most of the cases, we need not really solve the
problem. “Checking that whether the given statements are enough to solve the
problem” is only required than actually solving the problem.

For
example, see this one:

*Q1)What percent of 10 is 'x':*

*(1) x is 50 percent of 12*

*(2) 10 is 5 percent of x*

Here
note that each statement is individually sufficient to solve the problem. We
can find the value of ‘x’ from each statement independently and then get the
required answer ie., “what percent of 10 is x”. But don't get carried away with
solving. Just by seeing each of the statements, we can say that we can solve
the problem with the help of it. That’s all, that’s enough. The answer option
is "D"

Let
us see one more example here:

Q2)Find
the value of y:

(1)
3x-7y = 20

(2)
x+y = 2+y

Here
the ace is statement(2). It directly gives the value of x (of course, it is 2).
But is it sufficient to answer the Q'? It is asked to find the value of 'y',
not 'x'. Hence by using the value of 'x' from statement(2) and substituting it
in statement(1), we can get the value of 'y'. As both the statements are
required to solve this one, the answer option is "C".

But
suppose that it is asked for the value of 'x' in the main stem of the problem.
In that case, irrespective of statement(1), statement(2) alone is sufficient to
answer the Q’. And also, as statement(1) alone is not sufficient to answer the
Q’, the answer option is "B".

But
in some cases, it is required to solve the problem.
This arises in cases where the given statements seem to be enough to answer the
Q’ but if we really solve, it may result in "ambiguous" or "not
defined" or no answers. This is where GMAC can really trick us. For a given DS problem, “the
clarity on whether to go for solving or not” will come only through practicing
different types of problems and a careful noting of the special cases there on.

For
example, see this one:

Q3)What
is the value of 'x":

(1)
x-2y = 7

(2)
3x-5 = 6y

We
know that two unknowns (in this case x and y) can be solved by using at least
two equations. And hence we conclude that, both the given conditions are
required together to find the value of x. That’s where we commit mistake.

See
the second statement carefully. 3x-5 = 6y => 3x-6y = 5 => 3(x-2y)
= 5 => “x-2y
= 5/3”,
which is inconsistent with the first statement "x-2y = 7".
Hence, this Q’ cannot be answered even if we consider both the given statements
together. To get this clarity, as just now done on the second statement, we
need to shed a little on solving the given statements. I think we have no
doubts to mark the answer option as "E" for the above Q’.

Finally,
we will see one more example, where we need to really work on the given
statements to get answer for the Q’.

Q4)
Find the value of “5x-8y+z”:

(1)
2x+y-2z = 9

(2)
5x-y-3z = 6

A little brainstorming is required here whether we can
find two numbers with which if we respectively multiply the two statements and
do some manipulation to finally yield the value of “5x-8y+z”. In the case,
where we can find those two numbers, we can select the answer option “C”. But,
there is a possibility that we cannot find those two numbers ultimately and may
land to the answer option “E” as well. Try
this out…

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