Quants 4 (tough ones)

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praveen_84's picture
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Q1. If K = 231 x 319 , how many positive divisors of  k2 are less than k but do not divide K?
a. 1228                  b. 1028            c. 639                  d. 589

Q2. A triangle of side 20cm, 48cm and 52cm is cut into two pieces of equal area by a straight cut. What is the maximum possible sum of the perimeters of the two pieces (approximately)
a. 178cm               b. 190cm          c. 198cm                d. 218cm

Q3. How many integral solutions exist for the equation |x –105|  +  |y-303| <= 3?
a. 14                   b. 25                   c. 63                    d. None of these

Q4. A right circular cone is cut, parallel to its base into 5 slices. Heights of all slices are equal. By what percentage is the volume of the middle most slice lower than the volume of the largest slice?
a. 82.4%           b. 41.3%          c. 68.9%                 d. 55.3 %

Q5. Find the number of solutions for positive integers a, b and c such that a + b + c = 38 and a 2 + b 2 + c 2 = 722
a. 1                   b. 3                   c. 6                      d. None of these

Q6. A dice is rolled three times. Find the probability of getting a larger number than previous number each time.
a. 5/74               b. 7/54              c. 11/54                 d. 13/54

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jigar_er_civil's picture
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ans

Q6. A dice is rolled three times. Find the probability of getting a larger number than previous number each time.
a. 5/74               b. 7/54              c. 11/54                 d. 13/54

dice rolled three times
if getting 1 on first dice then
first dice       second       third
 1                   2             3/4/5/6
                      3             4/5/6/
                      4               5/6
                      5                 6
2                    3              4/5/6
                      4              5/6
                      5                6
3                     4                5/6
                      5                6
4                     5               6

so total 20 case

so probability=20/216 =5/54

Little Star
 

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Incognito (not verified)
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  K^2  factors  are 2, 3,

 

K^2  factors  are 2, 3, 2 x 3, 2^2 x 3, 2^3 x 3,. . . . . .2 x 3^2, 2 x 3^3. . . . . . .
We have to find out number of factors which are less than K.
 
Let any factor a is multiple of two numbers m and n (m=2 and n=3) and the factors are of the form m^p and n^q
 
For p=0
Possible values of q are 20, 21,. . . . . 38 = 19 numbers
i.e  3^20, 3^21. . . 3^18. . all these numbers are factors of K^2 which are small than K and K is not divisible by any of them
 
Similarly for p=1
Possible values of q are 20, 21. . . 37 = 18 numbers
. .. .
The sequence continues for p=2, 3. . . 17
For p=17
Only possible value of q is 20  = 1 number
 
From p=18 to 31 there ‘ll be only one possible value of q (i. e. 20) = 14 numbers
 
So total possible numbers for q>19 is
19 + 18 + . . . . 1 + 14 = 190 + 14 = 204
 
 
Similarly for q=0
Possible values of p are 32, 33. . . . .61 = 30
 
for q=1
Possible values of p are 32, 33. . . . .60 = 29
 
. . .
Total possible numbers =435
 
Answers = 639

 

nishit's picture
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The perimeter&lsquo;ll be

The perimeter‘ll be maximum when we cut the triangle with the base as the smallest side.
i.e we ‘ll cut the triangle at base 20 (BC) with a median drawn from point A.

Now the length of the medians

M20 = sqrt [ {2( 48)^2 + 2 (52)^2 – 20^2}/4]
      =49

So the sum of the perimeters of the newly formed two triangles

= 48 + 49 + 10 +
   52 + 49 + 10 = 218 cm

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jigar_er_civil's picture
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ans

Q4. A right circular cone is cut, parallel to its base into 5 slices. Heights of all slices are equal. By what percentage is the volume of the middle most slice lower than the volume of the largest slice?
a. 82.4%           b. 41.3%          c. 68.9%                 d. 55.3 %

ans is 68.9%

Little Star

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Incognito (not verified)
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Q3.

|x –105|  +  |y-303| <= 3?

Above is same as |A|  +  |B| <= 3

For |A|  +  |B| = 3      number of vals of A, B = 12
For |A|  +  |B| = 2      number of vals of A, B = 8
For |A|  +  |B| = 1      number of vals of A, B = 4
For |A|  +  |B| = 0      number of vals of A, B = 1

 So total number of solutions = 25

 btw do you see any pattern??

is there any easier method to solve this sort of question ???

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