Latest TCS Aptitude Question SOLUTION: 0,4,4,8.....the sum of unit digits of previous two numbers is next number.find the least value of n,such that Sn>2890

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(#M40153373) TCS Logical Reasoning question sum of sequece Keep an EYE

0,4,4,8.....the sum of unit digits of previous two numbers is next number.find the least value of n,such that Sn>2890

Asked In TCS saravanan (8 years ago)

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Siddhant Sengar  (8 years ago)

The Series is: 0,4,4,8,12,10,2,2,4,6,10,6,6,12,8,10,8,8,16,14,10,4,4,8,....................the series repeats after 21 terms and the sum of 21 terms is 158.
Since,Sn>2890 So, 158*18=2844
So total number of terms of this series to get 2844=21*18=378
Now we require 47 to get the sum greater than 2890,For that we must have the terms upto 4,4,8,12,10,2,2,4 means more 8 terms.
So we must have atleast (378+8)=386 terms of this series to get Sn>2890.
Hence,Least value of n=386,such that Sn>2890.

Is this solution Helpfull? Yes (9) | No   

Soham Dey  (8 years ago)

The series is 0,4,4,8,(8+4)=2,(2+8)=0,(0+2)=2,2,4,6,0,6,6,2,8,0,8,8,6,4(20th term),again it repeats from 0,4,4,8,2,0,....So sum of 20 terms=80,
Now sum must be >2890...So 2880/80=36....2880 is the sum of (36*20)=720 terms...but it must be greater than 2890,so 2880+0+4+4+8 will give 2896 which means number of terms is atleast 724...

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Bala Bhargav Kavuluri  (8 years ago)

Sum of Previous Two terms give next term.
Series : 0,4,4,8,12,20,32,52,84,136,220,356,576,932,1508,2440
n=17th term = 3948

Is this solution Helpfull? Yes (1) | No (8)  

MOHAMMAD ARSHAD  (8 years ago)

The Series is: 0,4,4,8,12,10,2,2,4,6,10,6,6,12,8,10,8,8,16,14,10,4,4,8,....................the series repeats after 20 terms the sum of frst 20 terms is 150 and sum of every next group of next 20 terms is 160 because the frst set of 20 terms starting with 0 and next sets will start with 10 . therefore 150+10= 160 for every next group of 20 terms
now 150+17(160)=2870 for (1+17)*20=360 terms
now we are 20 short of 2890 so we have to add further terms from the next group starting with 10 , so that total sum becomes> 2890 therefore 10+4+4+8= 22
hence total sum becomes 2892 . therefore total required terms are 20*18+4= 364

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Gaurav Maderna  (8 years ago)

This type of series known as fibnocci series.
there n=17.

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Lavina Rijhwani  (8 years ago)

The series is 0,4,4,8,12,10,2,2,4,6,10,6,6,12,8,10,8,8,16,14,10,4,4,8...... the series repeats after first 21 terms terms whose sum is 150
now 150 will come after 20 terms becoz 1st term is 0
Then, general term will- 150+2on>2890
n=2890-150/20
n=137
now since sum should be less then 2890 then n=137-1=136

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