Latest TCS Aptitude Question SOLUTION: 8+88+888+8888…. There are 21 “8”digits in the last term of the series. Find last three digits of sum. a.458 b.648 c.658 d.568

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(#M40165271) TCS Numerical Ability question number series Keep an EYE

8+88+888+8888…. There are 21 “8”digits in the last term of the series. Find last three digits of sum.
a.458
b.648
c.658
d.568

Asked In TCS Rajavenkatesh (6 years ago)

Unsolved Read Solution (10)

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Read Solution (10) :

Devendra Marghade  (6 years ago)

968

There is one 8 in first term, two 8s in second term, so twenty one 8s in 21st term.
While summing all terms of this series, we observe that, there are 21, 20 and 19 number of 8s in units, tens and hundredth place respectively.
So sum of all units digits=21x8=168, with carry 16 to tens place.
Sum of all tens digits=20x8=160 + 16 carry=176, so carry 17 to hundredth place.
Sum of all hundredth digits=19x8=152 + 17 carry=169, so carry 16 to thousand place.
Thus last 3 digits( hundred, tens, unit, ) of sum are 968

Is this solution Helpfull? Yes (15) | No   

Ayush saini  (6 years ago)

i donot even get 968 in options

Is this solution Helpfull? Yes (1) | No   

Smritika  (5 years ago)

568 option d

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

Tarun Gupta  (5 years ago)

Ans 648

For last digit 21×8=168. Insert 8 carry 16
For last 2 nd digit 21*8=168+ cqrry
168+16=184 insert 4. Carry 18
Last 3rd 21*8=168+18=186
Insert 6 carry 18

3rd&&2nd&&last
648

Is this solution Helpfull? Yes (1) | No (5)  

ganesh babu  (4 years ago)

8(1+11+111+...+111... 11)
=8*(1*1,1*2,1*3,....,1*19,1*20,1*21)
=8*(...121)last three digits
=.... 968 last three digits

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Charles.S  (6 years ago)

Answer is 968 . But the option given here is wrong.!!!

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Souvik  (5 years ago)

d
21 terms i.e. last digit of the sum is (21*8)= 8 and 16 in hand.
second last digit is (20*8)= 6 and 17 in hand

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  (5 years ago)

option d .568

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shanmukh  (5 years ago)

given that find last 3 digits sum
we are adding numbers so
take last 3 digits sum
888
888
888
ans 568(last 3 digits)

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gaurav singh  (4 years ago)

968
for last digit (8*21)=168 ,8 remains,16 carry
for 2nd last digit 16+(8*20)=176 ,6 remains ,17 carry
for 3rd last digit 17+(8*19)=169 ,9 remains ,16 carry
so final ans is ............968.............

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