Logical Reasoning - Number Series - Discussion

Look carefully for the pattern, and then choose which pair of numbers comes next.

1. 

28 25 5 21 18 5 14

[A]. 11 5
[B]. 10 7
[C]. 11 8
[D]. 5 10
[E]. 10 5

Answer: Option A

Explanation:

This is an alternating subtraction series with the interpolation of a random number, 5, as every third number. In the subtraction series, 3 is subtracted, then 4, then 3, and so on.

Raghavendra said: (Oct 11, 2010)  
Please give the details of solution of this question because I cannot understand the your given clue.

Star007 said: (Oct 19, 2010)  
Interpolation of a random number - 5 ? Explain this please.

Rohit T George said: (Nov 13, 2010)  
@star007

That is quite simple.

INTERPOLATION here means simply including the number without logic.

28 25 5 21 18 5 14
Here 5 is used as a median you can say remove the 5's
28 25 (diff 3)
21 18 (diff 3)
14 ? (diff 3)( ?=11)
Then the next number is 5 because of interpolation.

M.S.Kumar said: (Dec 11, 2010)  
Good easy question. Look at carefully.

Shreya said: (Jan 2, 2011)  
Excellent logic.

Raji said: (Feb 3, 2011)  
Nice solution given from rohit.

Sankari said: (Feb 11, 2011)  
Nice solution Rohit

Mohan Raviteja.Bollareddy said: (Feb 16, 2011)  
Please explain more because I can't understand this question.

Siva Prasad said: (Mar 5, 2011)  
This is really nice because here 5 is reapeted for every number of 2 numbers so if we get the differene between 2 numbers which are between 5 and 5 we can get the answer easily.

Praveen Pendli said: (Apr 1, 2011)  
Nice solution given from Rohit

Priyadarshini said: (Apr 26, 2011)  
Excellent solution given by rohit. Excellent logic question.

Sumit said: (Jul 7, 2011)  
Nice and easy solution thanks rohit.

Astha said: (Jul 12, 2011)  
Excellent logic Rohit.

Really appreciate,

Thanks.

Anitha said: (Aug 8, 2011)  
Nice explanation rohit..

Amit said: (Sep 8, 2011)  
Simple remove 5 and calculate number.

You find diffrennce of 3.

Preethi said: (Sep 11, 2011)  
Good rohit.

Shankari said: (Sep 12, 2011)  
I can't understand this problem.

Ganesh said: (Sep 21, 2011)  
Super Rohit.

Sanchit said: (Sep 26, 2011)  
Thanks rohit.

Mahesh said: (Oct 11, 2011)  
28-3=25 the answer is 3 after the number is 5 next substact the 21 and 18 the answer is 3 the randomly 5 is comes again we substaract 14-3=11 randomly the 5 comes the answer is A.

Akhila said: (Oct 12, 2011)  
Nice solution rohit.

Richa said: (Nov 26, 2011)  
Thanks rohit to give us explanation.

Balvir said: (Jan 4, 2012)  
28 (-3) 25 & 5
21 (-3) 18 & 5
14 (-3) 11 & 5

Ans (A) 11 5

Archana said: (Jan 6, 2012)  
Nice logic...
28 25 5 21 18 5 14
28-25=3 then
25-21=4 then
21-18=3 then
18-14=4 then
14-11=3 then answer is 11

One by one step we can minus by 3 and 4
Answer: 28 25 5 21 18 5 14 11 5

Omkar said: (Feb 2, 2012)  
That is quite simple.

INTERPOLATION here means simply including the number without logic.

28 25 5 21 18 5 14
Here 5 is used as a median you can say remove the 5's
28 25 (diff 3)
21 18 (diff 3)
14 ? (diff 3)( ?=11)
Then the next number is 5 because of interpolation.



28 (-3) 25 & 5
21 (-3) 18 & 5
14 (-3) 11 & 5

Ans (A) 11 5

Kailash Malav said: (Feb 28, 2012)  
Simply , look series first two number difference is 3 and second digit less than first digit than third digit is 5 and so on........

Rashmi Kumari said: (Mar 22, 2012)  
Difference of 1st and 4th number in series as 7,7,0 so put the value like that. So the next number in series are 11,5

28-21=7(1st no-4th no)
25-18=7(1st no-4th no)
5-5=0(1st no-4th no)
21-14=7(1st no-4th no)
18-11=7(1st no-4th no)
5-5=0(1st no-4th no)

Lovely said: (Sep 16, 2012)  
28-3=25 then 5
21-3=18 then 5
14-3=11 then 5
so answer is 11 5..

Sandip 5. 4 said: (Sep 20, 2012)  
Nice logic.

28 25 5 21 18 5 14
28-25=3 then
25-21=4 then
21-18=3 then
18-14=4 then
14-11=3 then answer is 11

One by one step we can minus by 3 and 4
Answer: 28 25 5 21 18 5 14 11 5

Rohit Vijay said: (Jan 22, 2013)  
This can be breakdown in a group series of three number:

First series is 28......21.......14 (diff 7).
Second series is 25.....18.......11 (diff 7).
Third series is interpolation of a random number 5...5..5.

So answer is
28,25,5
21,18,5
14,11,5
. . .

Sarbjit said: (Jun 17, 2013)  
28 (-3) 25 & 5.

21 (-3) 18 & 5.

14 (-3) 11 & 5.

Ajaykumar said: (Jun 25, 2013)  
Take first three number as one set. Then take second three number as another set. Here end number these two set is 5. So just leave. Then you have first set as 28 25.

Second set as 21 18.

Here the difference between First number from first set and first number from second set is 7.

Here third set first number is available as 14, then 18-7=11.

Add 5 as last number. Now answer is 14, 11, 5.

Veeresh said: (Jul 19, 2013)  
28 25 5 21 18 5 14

28-25 = 3 then
25-21 = 4 then
21-18 = 3 then
18-14 = 4 then
14-11 = 3 then answer is 11

One by one step we can minus by 3 and 4.

Answer: 28 25 5 21 18 5 14 11 5.

Birendra Singh said: (Jul 20, 2013)  
Now the answer 11, 5 because 28-25 = 3 21-18 = 3 14-3 = 11, 5.

Rama said: (Jan 8, 2014)  
I had easily understand this logic thank you for giving a simple explanation.

Sagar said: (Jan 30, 2014)  
28 25 5 21 18 5 14 11 5...

28-7=21.
25-7=18.
5 is common.

21-7=14.
18-7=11.
5 is common.

Than answer is 11 5.

Arul said: (Apr 8, 2014)  
28 25 5 21 18 5 14 11 5...

28-25 = 3+2 = 5.
21-18 = 3+2 = 5.
14-11 = 3+2 = 5.

So the answer is 11 5.

Ram Babu said: (May 22, 2014)  
Divide the given series into 3 sets of 3 no. each then find the diff of 1st two no. You will find that in all the 3 sets the diff 3 is common so obviously in the 4th set also the diff is 3 so see the no. Which will give 14 by adding 3 so that the diff is 3.

Kumar said: (Sep 23, 2014)  
After 2 numbers 5 is common.
28 25 difference b/t them 3.
21 18 21-18 = 3.
14 ? 14-? = 3 11, followed by 5.

Sai Vamshi said: (Oct 28, 2014)  
28 25 5 21 18 5 14

Count 3 numbers

28-21 = 7
21-14 = 7
And 25-18 = 7

18-? = 7/11
And 5 is came on

Next element is 5
Ans: 11 5.

Pradeep said: (Dec 4, 2014)  
28+25+5 = 58.
21+18+5 = 44.
14+.... = ?

58-44 = 14.
Then 44-14 = 30;

So check ans 14+11+5 = 30.

Mattoo said: (Jan 1, 2015)  
I looked at it as "28-25=3+2=5", then "21-18=3+2=5", then "14-11=3+2=5", and I arrived at the correct answer.

Uma said: (Apr 16, 2015)  
28-21 = 7.

The first figure subtract from the first second set of figure after 5 and which also applies to the next set of figure. i.e the 1st subtracted from the first of the other set and second from the second.

25-18 = 7.
21-14 = 7.
18-7 = 11.

Then 5 is repeated.

Harshit Singh said: (May 25, 2015)  
Its so simple. But logic is there.

De Vender Reddy said: (Jul 1, 2015)  
Reasoning are very logical questions.

Vks said: (Jul 23, 2015)  
Great logic.

Talwinder said: (Sep 28, 2015)  
Show the mind intelligence.

Jatadhari Sahoo said: (Feb 10, 2016)  
Its very simple question.

5 is common factor 2 number like:

28.....25....(5).

21.....18....(5).

14.....__....(5).

So 28---25 difference between them 3.

21---18.

= 21-18 = 3.

14 ? 11 - ? = 3 11, followed by 5.

Answer is 11.

Vanaja said: (Mar 1, 2016)  
Nice explanation.

Pallavi Krishna Gollapinni said: (Apr 7, 2016)  
28 - 3 = 25 & 5
25 - 4 = 21 & 5
21 - 3 = 18 & 5
18 - 4 = 14 & 5
14 - 3 = 11 & 5

It is a simple logic.

Vinay Juwantha said: (May 31, 2016)  
Easy to solve the series. Thank you all.

Surinder Singh said: (Jun 11, 2016)  
25 - 18 = 7.
21 - 14 = 7.
18 - 7 = 11.

Then 5 is repeated for every 3rd number.

Trilok Tak said: (Jun 14, 2016)  
28 25 5 21 18 5 14 ? ?

28 (-3) = 25 (Repeat)5.
21 (-3) = 18 (Repeat)5.
14 (-3) =11 (Repeat)5.

So,
28 25 5 21 18 5 14 11 5.

Jyotsana said: (Jul 10, 2016)  
I get the nice explanations. Thank you all.

Gowthami said: (Jul 18, 2016)  
28 - 3 = 25 & 5.
21 - 3 = 18 & 5.
14 - 3 = 11 & 5.

Surya said: (Jul 29, 2016)  
Thanks @Rohit.

Lipi said: (Aug 23, 2016)  
28 - (25) =3 5 =25 5.
21 - (18) =3 5 =18 5.
14 - (?) =3 5 = ? 5.
= 14 - (11) = 3 5 = 11 5 (ans).

Raghuram .M Pgdm 1 said: (Aug 24, 2016)  
Take difference of 3 for the preceeding number, placing 5 alternatively.

Ankita Debadarshi said: (Sep 15, 2016)  
I can't understand it. Please give me a solution in easy method.

Bhuva Vidhi said: (Sep 23, 2016)  
Thanks for all the explanations.

Ranju said: (Oct 3, 2016)  
5 is common, we subtract each number by 3.

K.Chandra Babu said: (Oct 28, 2016)  
5 is here just to confuse us .

Subtracting 3 from alternative numbers that is;
28 - 25 = 3.
21 - 18 = 3.
14 - 11 = 3.

Shashank Kumar said: (Jan 5, 2017)  
Well said @Veeresh.

Thank you.

Seshank said: (Feb 5, 2017)  
Nice @Rohit.

Sima said: (Mar 20, 2017)  
Thank you @Rohit.

Mayoo said: (Mar 29, 2017)  
Thank you @Rohit.

Akhilesh Kumar said: (Apr 17, 2017)  
You are right @Mahesh.

Utkarsh said: (May 25, 2017)  
As difference is;

25 - 18 = 7
18 - 7 = 11 as first digit,
And next will be common as 5.

Kamlesh Pache said: (Jun 15, 2017)  
Thank you all for the given explanation. I helps me a lot.

Gauravgupta said: (Jun 19, 2017)  
This is wrong way to solve this series.

Right way is here.

28-3=25.
25-4=21.
21-3=18.
18-4=14.

So first we subtract 3 n then 4 according to series we subtract 3 before 4 so.

14-3=11.

And 5 is interpolation.

Abhinay said: (Jul 27, 2017)  
MORE SIMPLE.

Use matrix 3*3.
28 25 5
21 18 5
14 11 5
06 04 5
Cross number series left -10 right -4.

Mennappan said: (Aug 20, 2017)  
median 5.
differ 3.
So 14-3=11.

Kinda Kumar said: (Aug 28, 2017)  
I cannot understand this. Please anyone this.

Minnu Abraham said: (Sep 3, 2017)  
Excellent logic @Rohit.

Sonia said: (Sep 13, 2017)  
Nice logic, Thank you @Rohit.

Liton said: (Sep 16, 2017)  
28 25 5 21 18 5 14 ? ?

28 - 7 = 21
25 - 7 = 18
5
21 - 7 = 14
18 - 7 = 11
5
14
Ans= 11.
Ans= 5.

Suneel said: (Oct 12, 2017)  
28 25 5 21 18 5 14 ? ?

28 - 7 = 21
25 - 7 = 18
5
21 - 7 = 14
18 - 7 = 11
5
14
Ans= 11.
Ans= 5.

Nikhilaadarsa said: (Nov 4, 2017)  
I can't understand the calculation.

Jitendra Rajput said: (Dec 23, 2017)  
Please give this solutoin.

Siddu Goud said: (Feb 28, 2018)  
How come answer is 11 5? PLease explain me, I am not getting it.

Annie said: (Aug 19, 2018)  
Nice logic, thank you @Rohit.

Sushant Kumar Behera said: (Sep 8, 2018)  
Thanks for explaining the logic of this.

Saurav said: (Oct 12, 2018)  
@All.

Look at the series carefully on 3rd postion of series "5" is repeating number and the common difference between 1st postion and 2nd postion number is 3 (.i.e. 28-25=3, 21-18=3 so next number should be 14-3=11), so ans for this question is 11 5.

Prabhat Singh said: (Oct 25, 2018)  
Please anyone help me by explaining the answer clearly.

Bhavya said: (Jan 26, 2019)  
Nice answer, Thanks @Rohit.

Kamaraj.S said: (Feb 4, 2019)  
5 is the interpolation of the random number.

Kpr said: (Sep 24, 2019)  
Nice explanation, Thanks @Rohit.

Glamour Dev said: (Dec 9, 2019)  
28 25 5 21 18 5 14
28-25=3
25-21=4
21-18=3
18-14=4

once first 3&4 18-11=3
answer=11.

Hitu said: (Dec 17, 2019)  
This question was very simple.

See, 28 25 5 21 18 5 14.

28-25=3.

5 was common in every 3 no.

Then 21-18=3.

5 common.

14-3=ans 11.

And 5 common.

Manoj Vardhan said: (Jan 21, 2020)  
Thanks for the clarification.

Soniya said: (Jan 22, 2020)  
Thanks @Rohit.

Roshinireddy said: (Sep 19, 2020)  
How we will get 115? I'm not able to understand, Please explain.

Pritish said: (Jan 27, 2021)  
@Roshinireddy.

So divide the list into a pair of 3 values each.

First, we get 28, 25, 5.
So for this 28-25 = 3 which is our main difference. Now they have put 5 randomly here without any logic.

The second pair is 21, 18, 5.
For this 21 -18 = 3 which is again our main difference and put 5 randomly after this.

Sakshi Nimbriya said: (Jun 20, 2021)  
Thanks for explaining @Rohit T George.

John said: (Jun 21, 2021)  
Thank you all for explaining.

Keerthi said: (Sep 1, 2021)  
Thank you everyone for explaining.

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