Logical Reasoning - Number Series - Discussion

@Harpreet Singh.

How he get 3..

11-8 = 3 21 is fixed.
18-15 = 3.

21 is common after every 2 number. So

8 11 21 15 18 21 22...

8+3 = 11 21.
15+3 = 18 21.
22+3 = 25 21.

So answer is 25 21.

There are two condition is here

1. Every 3rd number is 21
2. Difference between 2 and 1 number is 3.

In this way,
8-11=3
21
15-18=3
21
22-25=3. so the answer is 25 21

Thanks Sundar.

8+3 = 11
11+4 = 15
15+3 = 18
18+4 = 22
From above we can conclude as difference b/w first two no.is 3.
Third no. is interpolation, it is repeated as every third no.
so next pair is 25 21 (22+3 =25)

SOLUTION:
Here number 21 put as a interpolatn dat means only to confuse you. So just excluding that series will be like as:
8+3=11 (add 3 & interpolation 21)
15+3=18 (add 3 & interpolation 21)
Now 22+3 =25 (add 3 & interpolation 21)

So answer wil be B) 25 21 because 25 final anwer and 21 as a interpolation.

Hope now you get it.

I am not able to understand it please explain it as a layman could understand.

Actually it would be 25, 29. Adding 3 and alternate adding 4. So it should come 25, 29.

Really great, I can understand sundar's explanation thank you.

8,11,[21],15,18,[21],22,25,[21],29,32,[21]

1st no is 8,when 7 is added ,it gives 15 (4th number in series)
2nd no is 11 ,again when 7 is added,it gives 18(5th no in series)
21 is interpolated as every 3rd no.


4th no is 15 ,when 7 is added,it gives 22 (7th no)
5th no is 18,when 7 is added,it gives 25 (8th no)
again 21 is interpolated as 3rd no (here its 6th).


7th no is 22 ,when 7 is added,it gives 29 (10th no)
8th no is 25,when 7 is added,it gives 32 (11th no)
again 21 is interpolated as 3rd no (here its 9th).and so on.....