Infosys Puzzles
Hello ,
This post will contain all the puzzles from Infosys recruitment process. I will post 1 puzzle each day and solution at the end of the day..
Please try to solve it and we can have discussion here in the post.
This post will contain all the puzzles from Infosys recruitment process. I will post 1 puzzle each day and solution at the end of the day..
Please try to solve it and we can have discussion here in the post.
Replies

Radhika DeshpandeInfosys First Puzzle :
There is a escalator and 2 persons move down it.A takes 50 steps and B takes 75 steps
while the escalator is moving down. Given that the time taken by A to take 1 step is equal to
time taken by B to take 3 steps. Find the no. of steps in the escalator while it is staionary. 
Radhika DeshpandeNo Takers π
Alright, Here is the solution to the first puzzle ( I dont know whether this is correct or not) 
FrootyInfosys First Puzzle :
There is a escalator and 2 persons move down it.A takes 50 steps and B takes 75 steps
while the escalator is moving down. Given that the time taken by A to take 1 step is equal to
time taken by B to take 3 steps. Find the no. of steps in the escalator while it is staionary.
If A takes 1 step in one second, then B takes 3 steps in one second. If A takes t1 seconds to
take 50 steps, then B takes 150 steps in t1 seconds.
For B, to take 150 steps he requires t1 seconds,
then to take 75 steps he requires t1/2 seconds.
So now, s1=50, t1 = t1 & s2=75, t2=t1/2
ans= (s1*t2 ~ s2*t1) / (t1 ~ t2) which gives 100.
so 100 steps is the answer 
Radhika DeshpandeSecond Puzzle :
If the digits of my present age are reversed then I get the age of my son.If 1 year ago my
age was twice as that of my son.Find my present age ? 
Sagar0773..........

Radhika DeshpandeThats correct .
Father's age = 73 and Son's age = 37 
Radhika DeshpandeThird Puzzle :
There are 6561 balls out of them 1 is heavy.Find the minimum no. of times the balls have to be
weighed for finding out the heavy ball. 
Sagar07I think its 8... bcoz if u divide the balls in three parts, set of 2187 balls will be compared with set of 2187 balls, which one is heavier contains the heavy ball... if both of them weigh same dat means 3rd set contains heavy ball... that is 1st compaeison..
similarly, 2nd comparison will be between set of 729 balls
3rd243, 4th81, 5th27, 6th9, 7th3 n last will be between set of 1 ball..... 
Radhika Deshpande
PerfectSagar07I think its 8... bcoz if u divide the balls in three parts, set of 2187 balls will be compared with set of 2187 balls, which one is heavier contains the heavy ball... if both of them weigh same dat means 3rd set contains heavy ball... that is 1st compaeison..
similarly, 2nd comparison will be between set of 729 balls
3rd243, 4th81, 5th27, 6th9, 7th3 n last will be between set of 1 ball..... 
Radhika DeshpandeFourth Puzzle :
If i walk with 30 miles/hr I reach 1 hour before and if I walk with 20 miles/hr i reach 1 hour late.Find the distance between 2 points and the exact time of reaching destination is 11 am then find the speed with which it walks. 
born_star16Let original speed be v and time taken be t...
As distance between two points is constant,
30*(t1)=20*(t+1)=v*t
hence, v=24 mile/hr
t=5 hrs
distance between two points is 120 miles 
Radhika Deshpande
Thats Correct .born_star16Let original speed be v and time taken be t...
As distance between two points is constant,
30*(t1)=20*(t+1)=v*t
hence, v=24 mile/hr
t=5 hrs
distance between two points is 120 miles 
Radhika DeshpandeFifth Puzzle : 
Next number in the series is 1 , 2 , 4 , 13 , 31 , 112 , ? 
Radhika DeshpandeCome on guys . The above puzzle is not so tough. It was in Infosys paper. Please try to solve it

born_star16
I think the answer is 224 but not sure about it.FrootyCome on guys . The above puzzle is not so tough. It was in Infosys paper. Please try to solve it 
Radhika DeshpandeCorrect. The answer is 224.

Radhika DeshpandeSixth Puzzle 
Shahrukh speaks truth only in the morning and lies in the afternoon, whereas Salman
speaks truth only in the afternoon. A says that B is Shahrukh. Is it morning or afternoon and
who is A  Shahrukh or Salman? 
Sagar07I think its afternoon and A is salman...........
Will you please explain the logic behind the answer 224??? 
Radhika DeshpandeSagar07Will you please explain the logic behind the answer 224???
No number has digits more than 4. All of them are 1 , 2, 4, 8 , 16 , 32 , 64 converted to
numbers in base 5. 
Radhika Deshpande
The answer is correct.Sagar07I think its afternoon and A is salman........... 
Radhika DeshpandeSeventh Puzzle 
Sometime after 10:00 PM a murder took place. A witness claimed that the clock must
have stopped at the time of the shooting. It was later found that the position of both the
hands were the same but their positions had interchanged. Tell the time of the shooting
(both actual and claimed). 
Ayush Choudharywhat wud b the answer ?
π² 
Ankita KatdareThe time should be 00.50 am. π

Sughosh Deshmukhcan you please explain the solution to Fifth Puzzle : 
Next number in the series is 1 , 2 , 4 , 13 , 31 , 112 , ? 
Sughosh Deshmukhmay be the time is 11:10 pm actual and claimed to be 1:55pm...

Ramani Aswath
Let us assume that the time is some time soon after 10.00 pm. Because there is one more solution after that but before 12 midnight. What is needed is a situation where the hour hand is symmetric to the orientation of the minute hand.FrootySeventh Puzzle 
Sometime after 10:00 PM a murder took place. A witness claimed that the clock must
have stopped at the time of the shooting. It was later found that the position of both the
hands were the same but their positions had interchanged. Tell the time of the shooting
(both actual and claimed).
The hour hand moves 0.5 degree/min while the minute hand moves 6 degrees/ minute. At 10 the hour hand is 60 degrees from 12 and the minute hand is at 12. Let us assume that the hour hand moves by x degrees. This requires 2x minutes. In 2x minutes the minute hand moves 12x degrees.
For symmetry 60  x = 12x
13x = 60 from which x = 4.615
The time will be 9.23 minutes past 10.
With interchanged hands the time will be 1:50.8 AM 
Radhika DeshpandeAns:
Time of shooting = 11:54 PM
Claimed Time = 10:59 PM
SOLUTION ::
lets say
murder takes place at h2 : m2 , meaning h2 hrs and m2 minutes...
also let the claimed time be , h1 : m1
we know that angle swept by hr hand in 1 hr=30 degree
and angle swept by min hand in 1 min=6 degree
now as per question , the hr hand at one time will sweep same angle
with respect to standard 12 o clock position
as the minute hand from the other time ....
so we can get two eqns as ,
6 m1 = 30 h2 + (m2 / 2) ........................................(a)
6 m2 = 30 h1 + (m1 / 2) ........................................(b)
now adding (a) & (b)
11(m1 + m2) = 60 (h1 + h2) .............................(c)
also, we get from (a) & (b) ,
13(m1  m2) = 60(h2  h1) .............................(d)
now if we take , h1 & h2 as 10 & 11 repectively ,
from (c) we have m1 + m2 = 114.54 ................(e)
if we take , h1 & h2 as 11 & 12 repectively ,
from (c) we have m1 + m2 = 120
for that m1 = m2 =60 ....which would correspond to same time on clock ....hence not possible as per question ,
if we take , h1 & h2 as 11 & 12 repectively ,
from (c) we have m1 + m2 > 120 , which is not possible ...
and so on ...
we cant take h1 and h2 less than 10 , as murder takes place after 10 pm...
so putting the values of h1 and h2 in (d),
we get
m1  m2 =4.6153 ........................(f)
from (e) & (f) ,
m1= 59.577
m2=54.9623
hence the claimed time is 10 : 59.577
and the actual time of murder is 11 : 54.9623 
Radhika DeshpandeEighth Puzzle :
I bought a car with a peculiar 5 digit numbered licence plate which on reversing could
still be read. On reversing value is increased by 78633.Whats the original number if all
digits were different? 
Ramani Aswath
The angular position of the minute hand and the hour hand can have a mirror symmetry about the 12 o'Clock mark or the 11 o'Cock mark. The idea is that the person might claim that in the dim light he could not differentiate between the two hands. This can happen only if a mirror symmetry is present. The time will be 9.23 minutes past 10.FrootyAns:
Time of shooting = 11:54 PM
Claimed Time = 10:59 PM
With interchanged hands the time will be 1:50.8 AM. This is also a valid solution. 
Ramani Aswath
What is meant by reversed? Mirror image left to right (18 become 81) or upside down (58 becomes 28)?FrootyEighth Puzzle :
I bought a car with a peculiar 5 digit numbered licence plate which on reversing could
still be read. On reversing value is increased by 78633.Whats the original number if all
digits were different? 
Radhika DeshpandebioramaniWhat is meant by reversed? Mirror image left to right (18 become 81) or upside down (58 becomes 28)?
In this case upside down 
Sughosh Deshmukh
is the number 18256FrootyEighth Puzzle :
I bought a car with a peculiar 5 digit numbered licence plate which on reversing could
still be read. On reversing value is increased by 78633.Whats the original number if all
digits were different?
on reversing the number the new no. is 95281.
if the digits r written as seen on old digital calculators... 
Ramani AswathI spent a lot of time on this and ended up with too many theoretical blocks because of the condition that the reversed number has to be 78633 more than the original. It does not seem that any five digit number will meet all thew conditions.
I shall await for the answer. 
*pushkar*hey what types of puzzles are asked in infosys.? My friend told me to solve puzzles like sitting arrangement, sequential order etc from RS Aggarwal but you guys are sharing analytical puzzles :/

Kaustubh Katdare
I'm not sure whether there have been any recent changes to the way Infy conducts tests. But they always asked analytical and logical questions. You should be good at solving puzzles.*pushkar*hey what types of puzzles are asked in infosys.? My friend told me to solve puzzles like sitting arrangement, sequential order etc from RS Aggarwal but you guys are sharing analytical puzzles :/ 
PraveenKumar PurushothamanOnly 0 1 6 8 and 9 can be read upside down. So on rearranging these digits we get the answer as 10968.

BionicThe whole thing is confusin, please define the meaning of reversing...
Is is reversing 285 to 582
or
revesing 9 to 6
please xplain i wanna solve this puzzle pls... 
PraveenKumar Purushothaman
Reversing 9 to 6!BionicThe whole thing is confusin, please define the meaning of reversing...
Is is reversing 285 to 582
or
revesing 9 to 6
please xplain i wanna solve this puzzle pls... 
BionicI think this is the answer....
The original number is, 10968
when reversed you get 89601,
And when you take the difference between the two group of numbers, you get the increased 78633. 
PraveenKumar Purushothaman
Yes! πBionicI think this is the answer....
The original number is, 10968
when reversed you get 89601,
And when you take the difference between the two group of numbers, you get the increased 78633. 
akash.kasina
is the distance 120 miles????and the speed for reaching destination in exact time is 12miles/hr...is it correct???π¨FrootyFourth Puzzle :
If i walk with 30 miles/hr I reach 1 hour before and if I walk with 20 miles/hr i reach 1 hour late.Find the distance between 2 points and the exact time of reaching destination is 11 am then find the speed with which it walks. 
Anoop Kumar
120 miles with 24 mphakash.kasinais the distance 120 miles????and the speed for reaching destination in exact time is 12miles/hr...is it correct???π¨ 
akash.kasina
oh!!! niceπianoop120 miles with 24 mph 
ankur8819This is from my personal experience. π
There is a jailer and three prisoners in a room.Also there are 5 hats 3 Black and 2 white.
Each prisoner was made to wear a hat and guess the color of hat he is wearing..Each prisoner can see other's hat but not his.If a prisoner guesses the color of his hat correctly he is released else he is put back in Jail.Prisoner 1 guesses it wrong,prisoner 2 is sent to Jail.Prisoner 3 is released.How did he know ? 
Sagar07
Ankur, This kind of puzzle has been already solved.... Watch the thread "Princess Puzzle" by AKD...ankur8819This is from my personal experience. π
There is a jailer and three prisoners in a room.Also there are 5 hats 3 Black and 2 white.
Each prisoner was made to wear a hat and guess the color of hat he is wearing..Each prisoner can see other's hat but not his.If a prisoner guesses the color of his hat correctly he is released else he is put back in Jail.Prisoner 1 guesses it wrong,prisoner 2 is sent to Jail.Prisoner 3 is released.How did he know ? 
sowjitha
hmmm explanation pleaseFrootyThe answer is correct. 
Sagar07
Consider, its morning, so if A is shahrukh then the statement has to be true, but it says B is shahrukh..sowjithahmmm explanation please
and if A is salman then the statement has to be wrong, so, B can't be shahrukh, that means A is not salman..
So, its afternoon...
now, if A is salman then statement is true so, B is shahrukh....
So, A is Salman. 
sowjitha
But it is not mentioned that the statement is trueSagar07Consider, its morning, so if A is shahrukh then the statement has to be true, but it says B is shahrukh..
and if A is salman then the statement has to be wrong, so, B can't be shahrukh, that means A is not salman..
So, its afternoon...
now, if A is salman then statement is true so, B is shahrukh....
So, A is Salman. 
nibhanithe
the distance between two points is 125 mills...and it will walk with the speed of 25 mills/hour.......FrootyFourth Puzzle :
If i walk with 30 miles/hr I reach 1 hour before and if I walk with 20 miles/hr i reach 1 hour late.Find the distance between 2 points and the exact time of reaching destination is 11 am then find the speed with which it walks.
explantion
let that person takes x hours to reach the exact place at exact time...if its speed is 30mills/hour then it will cover the same distance as when its speed will be 20miils/hour then the distance covered will be same ,let this distance is "d"....then
with 30mills/hour it will take (x1) hour and with 20mills/hour it will take (x+1) hour and in both case distance will be same..so
30/(x1) =20/(x+1)
x=5 hours
and speed will be for reaching at exact time because time is 11am which is between 10am for 30mills/hour and 12pm for 20mills/hour...
(30+20)/(2) =25 mills /hour
so distance will be
d=25*5=125mills/hour
am i right?
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