Latest TCS Aptitude Question SOLUTION: Find the missing number 8 , 1 , 17 , 4 , 35 , 10 , 71 , ?, 143 22 20 12 21

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Find the missing number 8 , 1 , 17 , 4 , 35 , 10 , 71 , ?, 143
22
20
12
21

Asked In TCS Rimu Mukherjee (12 years ago)

Unsolved Read Solution (23)

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Read Solution (23) :

saurabh gupta  (12 years ago)

8,17,35,71,143 making a series and 1,4,10 making a series like
1*2+2=4
4*2+2=10
10*2+2=22
so missing number is 22

Is this solution Helpfull? Yes (22) | No (2)  

p nagaraju  (12 years ago)

its a mixed logic, 8*2+1=17,17*2+1=35......
and 1*2+2=4,4*2+2=10, 10*2+2=22'ans is 22

Is this solution Helpfull? Yes (1) | No   

Nishant   (12 years ago)

answer is 22.this is because when we multiply 8 by 2 and add 1,we get 17.similarly,17*2+1=35,35*2+1=71,71*2+1=143,so for other stream,we have
1*2+2=4,4*2+2=10,10*2+2=22,

Is this solution Helpfull? Yes (1) | No   

manish  (12 years ago)

ans:22
1 X 2=2+2=4
4 x 2=8+2=10
10 x 2=20+2=22

Is this solution Helpfull? Yes (1) | No   

Pradeep Poonia  (12 years ago)

Here we can see two series.....
1st is..
8,17,35,71,143,.......
and another we have..
1,4,10,?,......
in first series we adding multiple of 9*2^n-1 into the previous number as.
8+9*2^(1-1)=17
17+9*2^(2-1)=35
35+9*9^(3-1)=71.. and so on
and in another we are adding 3*2^(n-1) to the previous term as
1+3*2^(1-1)=4
4+3*2^(2-1)=10
10+3*2^(3-1)=22 and so on
so correct answer would be 22.

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

Vivek Gupta  (12 years ago)

Ans: 22
Details: because 1) as it is a series. like 8 is continuing with series 8, 17, 35, 71, and 143 as 8+8=16 now +1 it will give 17, then 17+17=34 now again +1 it will give 35 which is a series and so on.
2) the series which is to be answered is of 1, 4, 10, ?. Now in this problem again there is a series that difference between 1 and 4 is of 3 right, now double of 3 i.e. 6 is added to no. 4 to get 10 now double of 6 is to be added to get the answer i.e. 12 is to be added to no. 10 then result wud b 22 and continue the series.

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Rahul Sinha  (7 years ago)

Two series alternate
8 , 8*2 + 1, 17*2 + 1, .....
1, 1*2 +2 (4), 4*2+2 (10), 10*2+2 (22) ans

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saurabh middha  (12 years ago)

ans:22
first no.*2+no.of digits in next no.('0' not a digit)

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anju  (12 years ago)

take alternative terms......ie 1,3,5...etc and 2,4,6....etc
for 8,17,35...
2nd alternative term = 2*previous term+1
for 1,4,10..
4 = 1 + 3
10 = 4 + 3*2
? = 10+ 3*2*2
so ? = 22

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vedasruthi  (12 years ago)

Ans:20
Difference b/w 1st nd 2nd num is 7 nd 3rd nd 4th is (7+7-1).again the difference b/w 5th nd 6th is (13+13-1) nd again the unknown num shuld be (71-(25+25-1))i.e 20

Is this solution Helpfull? Yes | No (2)  

purushotham  (12 years ago)

they add 3 to 1 and they placed 4 alternativly and they increcing double 3 to 6 and they placed 10 they increcing double 6 to 12 and they add to 10 and the answer become 22

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vedasruthi  (12 years ago)

ans is 20 for sure

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Subhrangsu Bhowmik  (12 years ago)

8*2+1=17
(1+1)*2=4
17*2+1=35
(4+1)*2=10

......
?=22

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ARGHA BANERJEE  (12 years ago)

this is merging of 2 series.
1is:8,17,35,71,143
2nd 1is:1,4,10,?
so,8+9=17; Similarly,1+3=4;
17+2*9=35; 4+2*3=10;
35+2*18=71; 10+2*6=22.
71+2*36=143; So,it's 22.

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Ramlal  (12 years ago)

22. 17-8=9, 35-17=18, 71-35=36, 143-71=72 as same as 4-1=3, 10-4=6, so 22-10=12.

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Abhishek Sharma  (12 years ago)

Ans: 22
the odd positions number are of the pattern.. 8*2+1=17, 17*2+1=35, 35*2+1=71, 71*2+1=143
therefore,the even positions number are of the pattern 1*2+2=4, 4*2+2=10, hence 10*2+2=22.

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sandeep yadav  (12 years ago)

for odd place-(8*2)+1,17*2+1,...for even plces (4-1)=3difference now mul diff by 2 and add to no.3*2=6,now add 6 to 4=10,so 10-4=6and 6*2 =12 now add 12 to 10.answer is 22

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Sherin Sebastian  (12 years ago)

8, 17, 35, 71, 143 make a series
8 + 9 = 17
17 + 18 = 35
35 + 36 = 71
71 + 72 = 143 (the difference doubles each time)
The next series is 1, 4, 10, ?
1 + 3 = 4
4 + 6 = 10
10 + 12 = 22 (here too the difference doubles)
So ans is 22

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subhajeet  (12 years ago)

22, because the difference between the no.s in odd places, or the no.s in even spaces is getting doubled, i.e diff. of 1&4 is 3, diff. of 4&10 is 6, so diff. of 10 and next even no. has to be 12, so answer is 22.

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geethapriya  (12 years ago)

35*2=70+1=71, 10*2=20+2=22
so the ans is 22

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ANKIT PATEL  (8 years ago)

no*2+1, so ans is 22

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Anek Porwal  (7 years ago)

See the Question contains two series one is 8,17,35,71,143 : this we get by multipying by 2 and adding 1
(8 is the first number then next number is 8*2+1= 17 and so on), Coming to next series which is 1,4,10,?
(Here we nget next number by multiplying by 2 and then adding 2 like 1is the first number then next no. is 1*2=2+2=4 and so on )

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Pradeep jat  (4 years ago)

1+3=4
4+(3*2)=10
10+(6*2)=22

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