Placement Questions & Answers :: Infosys

Answer: 2342340

3 girls selected from 14 girls in 14C3 ways = 14! / 3! (14 - 3)! = 14! / 3!11! = 364 ways. (Formula used nCr = n! / r! (n-r)!)
And 7 boys selected from 15 boys in 15C7 ways = 15! / 7! (15 - 7)! = 15! / 7!8! = 6435 ways
So, possible ways = 364 x 6435 = 2342340 ways.

Answer: 2:03

Let's name both trains as A and B. Then,
Formula Used: √(A's speed) : √(B's speed) = √b : √a
√(A's speed) : √(B's speed) = √8 : √18 => 2√2 : 3√2 => 2 : 3.

Answer: 56

Given, he had 4 sons and 4 daughters.
Each son has 4 sons and 3 daughters and each daughter has 3 sons and 4 daughters.
Therefore total number of grandsons = 4x4 + 4x3 = 16 + 12 = 28
And total number of grand daughters = 4x3 + 4x4 = 28
Total number of grandchildren is 28+28 = 56.

Answer: 4

Let N be the number of daughters of the man.
Then each daughter has N-1 sisters.
Given that, each daughter has as many sons as her sisters.
That is, each of them has N-1 sons.
Number of grandsons of the man = N(N-1)
And the required product = N(N-1) x N = N x N(N-1) which lies between 40 and 50.
If N = 1 then N x N(N-1) = 0.
f N = 2 then N x N(N-1) = 2 x 2(1) = 4
If N = 3 then N x N(N-1) = 3 x 3 x 2 = 18
If N = 4 then N x N(N-1) = 4 x 4 x 3 = 48
If N = 5 then N x N(N-1) = 5 x 5 x 4 = 100
Therefore the possible value of N is 4.

Answer: 10 cm X 10 cm

To find the dimension, we have to find the number of pins on each of the sides of the square cardboard.
Similar to solutions of previous questions, there will be 4 corner pins. Corner pins when added with pins on edges should amount to 36 as given. Let the number of pins in between the corner pins on each of the edges be x.
Total Pins = 4 corner pins + 4 x number of pins on each of the edges in between corner pins
36 = 4 + 4x
32 = 4x or 8 = x
Therefore number of pins on any of the edge = 2 corner pins + 8 pins in between the corner pins = 10 pins.
Distance between each of the pins is 1 cm. Therefore the length of each of the sides = 9cm. Dimension of the square = 9 cm X 9 cm

Answer: 1000

Given, total number of players = 11
2 players(captain & goalkeeper)selected in 1 way.
Now, use the combination method, nCr = n! / r! (n-r)!
3 out of 5 can be selected in 5C3 ways = 5! / 3! (5 - 3)! = 10
Similarly, other 3 are selected from other two colleges.
Hence, total number of possible ways = 1 * 10 * 10 * 10 = 1000

Answer: 35 1/2 years.

I. During Marriage
Arunachalam's age = 29 years
Wife's age = 29 - 3.5 = 25.5 years
II. 20 years afterwards
Arunachalam's age = 29 + 20 = 49 years
Wife's age = 25.5 + 20 = 45.5 years
Let Son's age (20 years after marriage) = S
It is given that, 20 years after wedding, Arunachalam's age + Wife's age + S = 110
Or 49 + 45.5 + S = 110
S = 15.5 years
III. 40 years afterwards.
Since we have found that the son was 15.5 years old 20 years after marriage, adding 20 to 15.5 will give age of Kamalraj after 40 years.
Therefore answer = 15.5 + 20 = 35.5 years =35 1/2 years.

Answer: 6

Let A be the number of boys in Geetha's family.
let B be the number of girls in Geetha's family.
let C be the number of boys in Leena's family.
let D be the number of girls in Leena's family.
We have to find the value of A + D.
Since A number of boys are in Geetha's family, every brother will have A - 1 brother.
Since each of Geetha's brothers and Leena have equal number of brothers then A - 1 = C ------(1)
Since Leena has equal number of brothers and sisters, D - 1 = C -----(2)
Sub C = D - 1 in eq 1,we get
A - 1 = D - 1
A = D
we know the fact that addition of two equal numbers must be an even number.
among the given options 6 is the only even number.

Answer: 18 min.

Let Annie's speed be X km/hr.
Its given, Mugil is thrice as fast as Annie. Therefore Mugil's speed be 3X km/hr.
Also it is said Agil is twice as fast as Mugil. Therefore, Agil's speed = Mugil's speed x 2 = 6X km/hr.
Therefore ratio of their speeds = 6X : 3X : X = 6 : 3 : 1
For a given distance, the time taken will be inversely proportional to speed.
Therefore, Ratio of times taken by the three friends Agil, Mugil and Annie = 1/6 : 1/3 : 1 = 1 : 2 : 6
If Annie takes 6 minutes then Mugil takes 2 minutes.
If Annie takes 54 minutes then Mugil takes [2/6 * 54]= 18 minutes.
Hence the answer is 18 minutes.

Answer: X=1,Z=0

Simplifying, XY(Z+1)-ZY = XY
we get, XYZ + XY - ZY = XY
=> XYZ - ZY + XY = XY
=> XYZ - ZY = 0
=> XYZ = ZY
=> XZ = Z
=> XZ - Z=0
=> Z(X-1)=0
Above implies that either Z=0 or X-1=0 => x = 1