Logical Reasoning - Number Series - Discussion

In each series, look for the degree and direction of change between the numbers. In other words, do the numbers increase or decrease, and by how much

4. 

Look at this series: 22, 21, 23, 22, 24, 23, ... What number should come next?

[A]. 22
[B]. 24
[C]. 25
[D]. 26

Answer: Option C

Explanation:

In this simple alternating subtraction and addition series; 1 is subtracted, then 2 is added, and so on.

Abhiram said: (Oct 10, 2010)  
Another way to solve problem:

Sum alternatively it will get

22 + 1 = 23
23 + 1 = 24
21 + 1 = 22
22 + 1 = 23
so
24 + 1 = 25.

Pundik Vinayak said: (Aug 31, 2011)  
Here there is two no series following.

22 23 24 25 26 27.

21 22 23 24 25 26.

Santhikannan said: (Dec 2, 2011)  
22-1=21
21+2=23
23-1=22
22+2=24
24-1=23
23+2=25
(Therefor 23+2=25)

Vishal said: (Feb 18, 2012)  
We can see in in the pair of two number ...
(A)22 & 21
(B)23 & 22
(C)24 & 23
Answer in the series is (D) 25 & 24

Dipti said: (Mar 26, 2013)  
22-1=21.
21+2=23.
23-1=22.
22+2=24.
24-1=23.
23+2=25.

Hence answer =25.

Mahantesh said: (Apr 16, 2013)  
It is 1 and -2 series 22-21 = 1, 21-23 = -2 and so on

22-21 = 1
21-23 = -2
23-22 = 1
22-24 = -2
24-23 = 1
23-25 = -2

Answer is 25.

Ramesh said: (Dec 20, 2013)  
22 - 21.
23 - 22.
24 - 23.
therefore comes, 25.

Satrujit said: (Mar 27, 2014)  
-1,+2,-1,+2,-1,+2....So we can easily get the no is 25.

Jiya said: (Mar 12, 2015)  
There are alternative numbers 25.

= 22 23 24 -------.

And another alternative numbers:

= 21 22 23 24.

So the answer is 25.

Aaj said: (Jun 28, 2015)  
Why not 22? 22 21 23, 22 24 23, 22 27 23 can also happen right?

Divya said: (Jul 25, 2015)  
You can also see 1st letter is odd number and second 2 letters are even numbers.

Akashdeep said: (Dec 8, 2015)  
1 minus 2 plus.

Sudhansu said: (Jul 9, 2016)  
Series of -1 then +2, therefore the answer is 25.

Siraj Dal said: (Aug 15, 2016)  
There is a 2 no.of sequence.

22, 21
23, 22
24, 23
?(25), 24

Aditya Vamsi said: (Aug 24, 2016)  
Subtraction and adding series of the number 1and 2 takes place here.

M.Raghuram Pgdm 1 said: (Aug 24, 2016)  
It is simple and the logic is take 1 difference and add 2 alternatively.

Jhansi said: (Aug 24, 2016)  
Logic of this problem is alternate addition to the numbers.

K.Sujitha said: (Aug 24, 2016)  
For an alternative number, we have to add 1.

Sathishkumar said: (Nov 16, 2016)  
22 - 1 = 21.
21 + 2 = 23.
23 - 1 = 22.
22 + 2 = 24.
24 - 1 = 23.
23 + 2 = 25.

Hence answer = 25.

Zhia said: (Dec 16, 2016)  
Now, I understand this. Thanks :).

Ankur Sharma said: (Mar 8, 2017)  
This is soo simple, take all series in two pairs like, (22, 21), (23, 22), (24, 23),(25,24), ....

Shiv Dhakad said: (Jul 9, 2017)  
22-21 = 1,
21-23 = -2,
23-22 = 1,
22-24 = -2,
24-23 = 1,
23-25 = -2.

Kavi said: (Feb 24, 2018)  
22-1=21
23-1=22
24-1=23
25-1=24
So it comes as 21,22,23,24.

Heidi said: (Feb 28, 2018)  
Really well explained, thanks @Kavi.

Dayanidhi Parida said: (May 16, 2018)  
Thanks for explaining the solution.

Subhamita Dutta said: (Jun 14, 2019)  
Thanks for explaining the solution.

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