All The Best

All the best to all the CAT 2011 aspirants..

Cheers,
Rahul

Problem of the Day 12 Oct 2011

How many factors of  have last digit 2?

Problem of the Day 10 Oct 2011

Ten identical boxes of dimensions  are stacked flat on top of each other, with the orientation of each box being independent and random. If  is the probability that the height of the stack is  and , find . All units are in feet.

Problem of the Day 9th Oct 2011

In an increasing Arithmetic Progression, the product of the 5th term and the 6th term is 300. When
the 9th term of this A.P. is divided by the 5th term, the quotient is 5 and the remainder is 4. What is
the first term of the A.P.?
(a) 12                 (b) –40               (c) –16                     (d) –5

Problem of the day 8th oct 2011

Rohan is asked to figure out the marks scored by Sunil in three different subjects with the help of
certain clues. He is told that the product of the marks obtained by Sunil is 72 and the sum of the
marks obtained by Sunil is equal to the Rohan’s current age (in completed years). Rohan could not
answer the question with this information. When he was also told that Sunil got the highest marks
in Physics among the three subjects, he immediately answered the question correctly. What is the
sum of the marks scored by Sunil in the two subjects other than Physics?

(a) 6                  (b) 8                (c) 10               (d) Cannot be determined

Problem of the day 7th Oct 2011

Ten books are arranged in a row on a bookshelf. A student has to select three out of these ten books
in such a way that no two books selected by him must have been lying adjacently. In how many
ways can he make the selection?
(a) 56                                (b) 64                           (c) 72                    (d) None of these

Problem of the Day 6th Oct 2011

If xΔ(y +1) = yΔ(x +1), xΔ x = 1 and (x − y)Δ(x + y) = xΔ y, then what is the value of 1001Δ1?
(a) 1000                   (b) 100                    (c) 10                 (d) 1

Problem of the day 5th Oct 2011

The set S contains nine numbers. The mean of the numbers in S is 202. The mean of the five smallest of the numbers in S is 100. The mean of the five largest numbers in S is 300. What is the median of the numbers in S?

Problem of the Day 4th Oct 2011

Find  and , where the variables are natural numbers:

Problem of the Day 3rd Oct 2011

How many ordered pairs of positive integers  satisfy the system



where  and  denote the greatest common divisor and least common multiple of  and , respectively?


(A)   0        (B) 1         (C)  2            (3) More than 2

Problem of The day 2nd Oct 2011

Let [x] and {x} respectively denote the integer and fractional part of of a real number x. If {n} + {3n}=1.4, find the sum of all possible values of 100{n}.

(A) 180           (B) 145                (C) 85      (d) 102

Problem of the Day 29 Sept 2011

Let a, b, c be three distinct odd natural numbers. Which of the following can be the sum of the squares of a, b and c?

(a) 3333                            (b) 5555                                (c) 9999                        (d) 7777

Like us on Facebook!

Problem of the day 26 Sept 2011

Let a₁= 2 and a_n+1 = 2a_n + 1. Find the least value of a_n which is not prime.

(a) 47                  (b) 4                    (c) 5                 (d) 95

Like us on Facebook!

Problem of the Day 25 Sept 2011

Let P be the set of all the vertices of a regular polygon of 25 sides with its center at C. How many triangles have vertices in P and contain the point C in the interior of the triangles?


Please like us on Facebook.

Problem of the Day 24 Sept 2011

In triangles ABC and DEF, DE=4AB, EF=4BC, FD=4CA The area of triangle DEF is 360 units more than the area of triangle ABC. Compute the area of triangle ABC



Please like us on facebook. Click the like button on the right.

Problem of the Day 23 Sept 2011

Darryl has a six-sided die with faces 1; 2; 3; 4; 5; 6. He knows the die is weighted so that one face
comes up with probability 1/2 and the other five faces have equal probability of coming up. He
unfortunately does not know which side is weighted, but he knows each face is equally likely
to be the weighted one.

He rolls the die 5 times and gets a 1; 2; 3; 4 and 5 in some unspecified order. Compute the probability that his next roll is a 6.



Please like us on facebook.

How to use the options to maximize scores in QA/DI/LR in IIM CAT

The good thing about CAT is, that it is not a mathematics test. So, it helps that you know the process and the steps but you should be smart and try to minimize the work. This is why there are options to help you. A smart use of options will save a lot of time and help you increase your score.

Some examples

Two different two-digit natural numbers are written beside each other such that the larger number is written on the left. When the absolute difference of the two numbers is subtracted from the four-digit number so formed, the number obtained is 5481. What is the sum of the two two-digit numbers?


(a) 70         (b) 71                (c) 72                         (d) 73


Now it is pretty much obvious the number is of the form 55xy
To find xy we can just subtract 55 from the options which gives xy= 15, 16, 17, 18

If you are lucky you will start with 73 and you will know it is right, else even if you start with 15, you will soon reach 18 and get your answer.


The direct method will be a bit long.

 Let n be the total number of different 5-digit numbers with all distinct digits, formed using 2, 3, 4, 5 and 6 and divisible by 4. What is the value of n?

1] 44 2] 32 3] 36 4] 38 5] 40

Permutations & Combinations is probably the most ‘hated’ topic. However, if you understand the basics and use logic, then it is the most fun-filled topic of all. Let us get to this question. As mentioned, we need to find out the 5 digit numbers divisible by 4 formed by the digits given in the question. To be divisible by 4, the last 2 digits should be divisible by 4. So to arrive at the answer, the first step is to find out combinations of the 2 digits from 2,3,4,5 & 6 that are divisible by 4 – eg: 24. Then, for each such combination, the last 2 digits are fixed. The remaining 3 digits can be arranged in 3! Ways = 6 ways. So the answer would be - 6 multiplied by the total no. of combinations of 2 digits divisible by 4. The answer necessarily should be a multiple of 6 and therefore the answer is 36 – option [3]. We just got lucky here, by the way, since there is just one option that is divisible by 6!

Problem of the Day 22 Sept 2011

Susan plays a game in which she rolls two fair standard six-sided dice with sides labeled one through six. She wins if the number on one of the dice is three times the number on the other die. If Susan plays this game three times, compute the probability that she wins at least once.

Problem of the Week 21 Sept 2011

The leftmost digit of an integer of length 2000 digits is 3. In this integer, any two consecutive digits must be divisible by 17 or 23. The 2000th digit may be either a or b. What is the value of a+b?

Problem of the Day 19 September 2011

Two mathematicians take a morning coffee break each day. They arrive at the cafeteria independently, at random times between 9 a.m. and 10 a.m., and stay for exactly  mintues. The probability that either one arrives while the other is in the cafeteria is  and where  and  are positive integers, and  is not divisible by the square of any prime. Find