Latest TCS Aptitude Question SOLUTION: 1,-3,2,-4,3,-5.... upto 2000 terms. find the average

• Placement Papers
• /
• TCS
• /
• Numerical Ability
• /
• Averages

TCS Question Papers: TCS Interview Experience(90) TCS Company Profile

(#M40033919) TCS Numerical Ability question Average Keep an EYE

1,-3,2,-4,3,-5.... upto 2000 terms. find the average

Asked In TCS JAMES (10 years ago)

Solved Pu Read Solution (14)

Is this Puzzle helpful?   (11)   (2) Submit Your Solution Averages

Read Solution (14) :

Pu  (10 years ago)

((1-3)+(2-4)+(3-5)+...2000 terms)/2000 => (-2-2-2... 1000 terms)/2000 => -2000/2000=>-1

Is this solution Helpfull? Yes (36) | No (1)  

AVINASH REDDY BHIMIREDDY  (10 years ago)

here in the question the average is asked for up to 2000 terms.
so up to 2000 terms will be

{1,-3,2,-4,3,-5,.........,1000,-1002}

so if we add them like this
{(1-3)+(2-4)+(3-5)+.........+(1000-1002)}
this will a sum of
{-2-2-2-2-......-2} for thousand times
i.e. {1000*(-2)}
therefore the sum is -2000
the average will be -2000/2000 = -1

Is this solution Helpfull? Yes (7) | No (1)  

venkata swamy  (10 years ago)

it is one of the ques in the today's tcs off campus.

Is this solution Helpfull? Yes (2) | No   

Benit Jose  (10 years ago)

todays tcs question. options was 1,-1,2,-2

Is this solution Helpfull? Yes (2) | No (1)  

Shruti  (9 years ago)

ans is -1.
1-3=-2 2-4=-2 3-5=-2 .hence there are total of 1000 (-2s) when the no. of terms is 2000 so the avg. will be {1000*(-2)}/2000=-1

Is this solution Helpfull? Yes (2) | No   

amrita  (9 years ago)

1,2,3.....1000terms+-3,-4,-5......1000term
S(n)=n/2(2*a+(n-1)d)
1000/2(1*2+(1000-1)1)+1000/2(2(-3)+(1000-1)-1)
=-2000
hence,avg=-2000/2000=-1

Is this solution Helpfull? Yes (1) | No   

Kundan Dhande  (10 years ago)

@PU the question is asking that upto 2000
so the last three terms should be 1999 -2001 2000
so i think we have to consider -2001 also
this is because see in the question if the series ends on 3 then the previous number is -4 so if the series will end on 2000 then the previous number should be -2001
and after that we have to find the ans..

Is this solution Helpfull? Yes | No (2)  

sreekanth  (9 years ago)

consider 1,2,3...2000 series;-3,-4,-5 ...-2002 series ;these two series are arthematic series so
(1+2000)/2=1000.5
(-3-2002)/2=-1002.5
so (1000.5-1002.5)/2 =>-2/2=-1

Is this solution Helpfull? Yes | No   

vishal  (9 years ago)

(1-3)+(2-4)....difference is -2
so by 2000-2 = 1198
so that (1, -3, 2 , ...2000,-2002)
(1-2002)/2000=-1

Is this solution Helpfull? Yes | No   

dandaraviteja  (9 years ago)

cross verify for 4 and 6 terms
1-3+2-4=-4/4=-1
(1-3+2-4+3-5)/6=-1

Is this solution Helpfull? Yes | No   

ANKITA DEB  (9 years ago)

((1-3)+(2-4)+(3-5)+....till 2000terms)/2000
=(-2-2-2....till 1000terms )/2000
=-2000/2000
=-1 ans

Is this solution Helpfull? Yes | No   

sai neelesh  (9 years ago)

as the difference is 2 between two terms there are 1000 terms if we conside r two ata atime
-2*1000/2000=-1

Is this solution Helpfull? Yes | No   

siddharht kapoor  (9 years ago)

first take an average of th follow digits=(1-3+2-4+3-5) then result is=-6
now take average is (1-3+2-4+3-5)/6=-6/6= -1 ans

Is this solution Helpfull? Yes | No   

Preksha Srivastava  (6 years ago)

-2*1000/2000=-1

Is this solution Helpfull? Yes | No   

Please Login to Read Solution.