CAT Quantitative Ability

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CAT Preparation

• Shortcuts for Quants Section

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Overview of Quants Section
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• The perception with a lot of students with
  regards to CAT is that CAT is for Engineers. A
  non engineer finds it difficult as there is a lot
  of Math in CAT. Most of the students tend to give
  up on CAT as they cant find how to break the
  Math conundrum. They learn formulae by rote and
  try to use the formulae in different sums in the
  Mocks only to realize that their scores are not
  improving.

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Topics to be done
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Example 1

• Example Lets take a question from CAT08
• A shop stores x kg of rice. The first customer
  buys half this amount plus half a kg of rice. The
  second customer buys half the remaining amount
  plus half a kg of rice. Then the third customer
  also buys half the remaining amount plus half a
  kg of rice. Thereafter, no rice is left in the
  shop. Which of the following best describes the
  value of x?
• (1) 2 x 6  (b) 5 x 8  (c) 9 x 12  (d)
  11 x 14 (e) 13 x 18
• Solution
• Usually students who are used to formulae and
  equation will tend to use x as the initial amount
  of rice and try to form an equation to solve the
  sum. A better way would be to go reverse way. Say
  the last person has no rice left after he was
  given half the rice plus half a kg of rice. So he
  would have (01/2) x 2 1Kg before the last
  customer came in. Similarly before the second
  customer had come the shopkeeper would have (1
  ½) x 2 3. Before the first customer came in the
  shopkeeper would have (3 ½) x 2 7kgs which is
  the answer.

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Example 2

• X v(4 v(4 - v(4 v(4 .)))) to infinity.
  Then x equals  (CAT05)
• (a) 3  (b) (v13 1)/2  (c) (v13 1)/2  (d) v13
• Solution
• We know that v4 anything will be less than 2.
  So we get v 4 (less than 2). Which should be
  more than 2 but less than 2.5. The only option
  that satisfied is c option with v13 is
  approximately 3.5. So (3.5 1)/2 2.25. The
  same sum can be solved by formulae but that will
  take time.

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Example 3

• SUMMARY OF PERMUTATIONS COMBINATIONS

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Contd.
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How to Increase speed in maths?

• Keep away from difficult formulae. The less
  formulae you know the better it is. Obviously you
  need to know basic formulae like 1 2 3
  n(n1)/2 or (ab)2 a2 2ab b2. But dont
  get into any new formulae you have not heard of.
  It will only slow you down.
• Learn all the tables,squares,fractions,percentages
  which will also help you in data interpretation.

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Speed Maths

• Square of any two digit number Easiest method
• Let me explain this trick by taking examples672
  62722067 3649840
  4489similarly252 22522025
  425200 625Take one more example972
  92722097 81491260 9409

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Speed Maths

• How fast can you multiply the following
  numbers11 19 ?
• 27 23 ?
• 39 31 ?
• According to this trick, the first part of the
  numbers should be the same
• example,
• in 11 19, 27 23, 112 118, 124 126 the
  first part of the numbers are same,
• now the second condition is that the second part
  of the numbers should have the sum exactly 10 as
  in
• 11 19, 27 23, 112 118, 124 126
• Only when both conditions are fulfilled, then
  the method works.
• Alright, now according to the method multiply the
  first part of the number with 1 more than the
  number, i.e. if first part is 11, then multiply
  with 12, if its 1 then with 2, and so on.
• 11 19 2_ , 112 118 132_
• Next, multiply second part of both the numbers
  together to get second part of the answer, if it
  comes a single digit then put a zero in front
  else no need for zero, like in
• 11 19 209 , 112 118 13216

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What can be done to improve maths?

• Go back to all the mocks you have solved and go
  through the questions again to search for better
  ways of solving. If you find it write it down
  next to the sum so that when you go through the
  paper again you could remember the methods you
  used. Also once before the exam go and check the
  shortcut methods you used to solve the sums. This
  would ensure that it is fresh in your mind when
  you solve the paper.
• -  Continue writing the usual Mock Papers and
  analyze it. Try to get better ways of solving it
  than that provided by explanatory answers.
• -  Go through the 5 previous CAT papers and see
  if you could get methods to solve the questions
  there. Understand this that CAT does not repeat
  questions, but the methods used to solve CAT sums
  can be repetitive as shown in the examples.

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