Latest TCS Aptitude Question SOLUTION: 8+88+888+.....+8888........8888. There are 21 “8” digits in the last term of the series. Find the last three digits of the sum.

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8+88+888+.....+8888........8888. There are 21 “8” digits in the last term of the series.
Find the last three digits of the sum.

Asked In TCS logesh (9 years ago)

Solved thameem Read Solution (24)

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Read Solution (24) :

thameem  (9 years ago) Best Solution

21*8=168 carry 16
20*8=160+16=176 carry 17
19*8=152+17=169
the value is 968

Is this solution Helpfull? Yes (80) | No (13)  

priya maurya  (9 years ago)

when we write this in sumation form...then.....
At ones place 8 comes 21 times ....so...8*21=168
At tens place 8 comes 20 times......so...8*20=160...but in this 16 is added, came from ones addition..so after adding 176 comes
At hundred place 8 comes 19 times....so...8*19=152..after adding 17 from previous.....169 comes....so last three digit is.........968

Is this solution Helpfull? Yes (22) | No (4)  

dee hack kr  (9 years ago)

8(1+11+111+1111+....)=8(............2121)=.......968

Is this solution Helpfull? Yes (20) | No (5)  

deksha sri  (8 years ago)

19th term->....88
20th term-> ...888
21th term->....8888
adding last three digits of every term we get answer:568.

Is this solution Helpfull? Yes (13) | No (6)  

Arun kumar prajapati  (9 years ago)

Since. 8+88+888+8888+88888+888888+.........+"8" 19 times +"8" 20 times+"8" 21 times= 8[123456.......192021]
Hence last three digit=8(.....19+20+21)= .... 968

Is this solution Helpfull? Yes (7) | No (3)  

Himanshu gaur  (9 years ago)

21*8= 168 carry 16
20*8=160+16(add previous carry)=176 now carry 17
19*8=152+17=169
Thus last 3 digit are 968

Is this solution Helpfull? Yes (6) | No (2)  

prasanna  (9 years ago)

@ gopinath for 21*8=168 carry 16 = 168
20*8=160+16=176 carry 17= 176
19*8=152+17=169 = 169
take last units digit , 968

Is this solution Helpfull? Yes (4) | No (1)  

AMIT KUMAR  (9 years ago)

968
21*8=16 8, 8
20*8+16=17 6 6
19*8+17=16 9 9
so answer is 968

Is this solution Helpfull? Yes (3) | No (2)  

Akanksha Tripathi  (9 years ago)

888*19=16872
16872+88+8= 16968
so last three digits will be 968

Is this solution Helpfull? Yes (3) | No   

Akash  (8 years ago)

568 is the correct answer....968 is not even in the options

Is this solution Helpfull? Yes (3) | No   

tejaswi  (9 years ago)

can anyone plz tel me how wil we get 968

Is this solution Helpfull? Yes (2) | No   

shiek javed ahamed  (8 years ago)

1
11
111
1111
-------------------
121
--------------------
121*8=968

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

Lakkireddy Rama Narayana Reddy  (7 years ago)

(2)
19th...............8 8 8
20th...............8 8 8 8
21st................8 8 8 8 8
--------------------------------------------
5 6 8
--------------------------------------------

Is this solution Helpfull? Yes (1) | No   

esha dian  (9 years ago)

please can any one explain

Is this solution Helpfull? Yes | No   

jeyshri  (9 years ago)

can anyone explain this clearly..how the carry comes??

Is this solution Helpfull? Yes | No   

lakshmi naga sownika  (9 years ago)

8+88+888......=8/9((10(10^n-1)/9)-n)
as n=21
by solving we get 9.87654321*10^20
hence sum of last three digits is 0+0+0=0

Is this solution Helpfull? Yes | No (8)  

shubhrata shukla  (9 years ago)

But how did 968 come??

Is this solution Helpfull? Yes | No   

Rohit Mharir  (9 years ago)

how carry comes?????eny 1 explain plz

Is this solution Helpfull? Yes | No (1)  

Gopinath  (9 years ago)

Can any1 explain this sum ???

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sanghita sengupta  (9 years ago)

please show how 968 is coming...please show the calculations even.....
nt getting clear.

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Gopinath  (9 years ago)

pls explain in an easy way how u got that last 968 ????

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DEEPIKA REDDY GUNUKULA  (8 years ago)

answer is 968

Is this solution Helpfull? Yes | No   

vikaskumar jaisal  (8 years ago)

8+88+888+888888+888.....8888
becouse every 8 is becouse it is multiplied by last two and added by last two

Is this solution Helpfull? Yes | No (1)  

Sneha Naluvala  (5 years ago)

8*(19+20+21)=480

Is this solution Helpfull? Yes | No (1)  

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