Tips on Cracking Reasoning Questions Based on Data Sufficiency

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5 TIPS on cracking Aptitude Questions of Data
Sufficiency type
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Tip 1 Do Not solve the problems.
Analyze the information provided Do not solve
the question using the information at hand .

• Question Two towns are connected by railway. Can
  you find the distance between them?
• I. The speed of the mail train is 12 km/hr more
  than that of an express train.
• II. A mail train takes 40 minutes less than an
  express train to cover the distance.
• I alone sufficient while II alone not sufficient
  to answer.
• II alone sufficient while I alone not sufficient
  to answer.
• Either I or II alone sufficient to answer.
• Both I and II are not sufficient to answer.
• Both I and II are necessary to answer
• Solution
• Let the distance between the two towns be D km.
  Let the speed of the express train be S km/hr.
  The speed of the mail train is S12 km/hr.
• Creating an equation using I and II
• D/(S12) (D/S) (2/3) because 40 minutes
  2/3 hrs
• Dont try to solve this equation. There is one
  equation with two variables and cannot be solved.
  Hence, the correct answer is D.

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Tip 2 Represent the given information visually
on paper to easily process it.

• Question How many children does M have ?
• I. H is the only daughter of X who is wife of M.
• II. K and J are brothers of M.
• I alone sufficient while II alone not sufficient
  to answer.
• II alone sufficient while I alone not sufficient
  to answer.
• Either I or II alone sufficient to answer.
• Both I and II are not sufficient to answer.
• Both I and II are necessary to answer.
• Solution

From I, we have that H is the only daughter of M.
But that does not mean that M has no son. Thus,
the information is not enough to answer the
question. II does not give tell us anything about
Ms children. Thus, the correct answer is D.
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Tip 3 Do not make assumptions that cannot be
justified by the given statements.

• Question How many ewes (female sheep) in a flock
  of 50 sheep are black?
• I. There are 10 rams (male sheep) in the flock.
• II. Forty percent of the animals are black.
• I alone sufficient while II alone not sufficient
  to answer.
• II alone sufficient while I alone not sufficient
  to answer.
• Either I or II alone sufficient to answer.
• Both I and II are not sufficient to answer.
• Both I and II are necessary to answer
• Solution
• Do not assume that the proportion of white black
  sheep is uniform across rams and ewes. We know
  from (I) that there are 40 ewes but we do not
  know that 40 of ewes are black.
• Hence the right answer is D

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Tip 4 Use Venn Diagrams when possible.

• Question Of the 70 children that visited a
  certain doctor last week, how many had neither
  caught cough nor cold?
• 40 of 70 had cough but not cold.
• 20 of 70 had both cough and cold.
• I alone sufficient while II alone not sufficient
  to answer.
• II alone sufficient while I alone not sufficient
  to answer.
• Either I or II alone sufficient to answer.
• Both I and II are not sufficient to answer.
• Both I and II are necessary to answer.
• Solution

?
40
Cold
Cough
As we see in the Venn diagram, neither is
sufficient but together, they are enough to solve
the question. Hence, the answer is E.
20
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Tip 5 Typically the choices A through E tend to
be the same.

• We have already seen from the above examples that
  the choices are always given as follows
• I alone sufficient while II alone not sufficient
  to answer.
• II alone sufficient while I alone not sufficient
  to answer.
• Either I or II alone sufficient to answer.
• Both I and II are not sufficient to answer.
• Both I and II are necessary to answer.
• So you can save time by just skimming over the
  choices superficially..

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