Logical Reasoning - Number Series - Discussion
Discussion Forum : Number Series - Type 1 (Q.No. 6)
Directions to Solve
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
6.
Look at this series: 21, 9, 21, 11, 21, 13, 21, ... What number should come next?
Answer: Option
Explanation:
In this alternating repetition series, the random number 21 is interpolated every other number into an otherwise simple addition series that increases by 2, beginning with the number 9.
Discussion:
45 comments Page 4 of 5.
Titus said:
1 decade ago
21-9=12
12+9=21
21-11=10
10+11=21
21-13=8
8+13=21
21-15=6
6+15=21
21-17=4
4+17=21
The numbers increase by 2 in ascending order. Therefore the answer is 15.
12+9=21
21-11=10
10+11=21
21-13=8
8+13=21
21-15=6
6+15=21
21-17=4
4+17=21
The numbers increase by 2 in ascending order. Therefore the answer is 15.
Tanweer said:
1 decade ago
21-12 = 9.
21-10 = 11.
21-8 = 13.
21-6 = 15.
21-10 = 11.
21-8 = 13.
21-6 = 15.
BHUMIT DOBARIYA said:
1 decade ago
ODD POSITION : 21 21 21 21.
EVEN POSITION : 9 11 13 15 (ADD 2).
EVEN POSITION : 9 11 13 15 (ADD 2).
Rincy said:
1 decade ago
If we add 21+9 = 32.
9+21 = 32.
21+11 = 34.
11+21 = 34 it increases by 2 so the next number should be 36 21+15=36.
So answer 15.
9+21 = 32.
21+11 = 34.
11+21 = 34 it increases by 2 so the next number should be 36 21+15=36.
So answer 15.
PRAVEEN said:
1 decade ago
21 is the randomly executed and 9, 11, 13 digits are increased by the value 2, so the answer is 15.
Anand said:
1 decade ago
2nd, 4rd, 6th number are added +2 .
Hence answer is 15.
2nd number is 9 +2=11.
4th number is 11+2= 13.
6th number is 13+2=15.
Hence answer is 15.
2nd number is 9 +2=11.
4th number is 11+2= 13.
6th number is 13+2=15.
Sahil suman said:
1 decade ago
It can also be done by.
9+2=11, 11+2=13, 13+2=15 answer is 15.
9+2=11, 11+2=13, 13+2=15 answer is 15.
Surya said:
1 decade ago
1st, 3rd, 5th, 7th place no's are same
2nd,4h,6th place are adding 2
9+2=11
11+2=13
13+2=15
ans=15
2nd,4h,6th place are adding 2
9+2=11
11+2=13
13+2=15
ans=15
Abi said:
1 decade ago
Hi, it cab be easily solved.
1st, 3rd, 5th, 7th place no's are same
2nd,4h,6th place are adding 2
9+2=11
11+2=13
13+2=15
ans=15
1st, 3rd, 5th, 7th place no's are same
2nd,4h,6th place are adding 2
9+2=11
11+2=13
13+2=15
ans=15
Jio said:
1 decade ago
It can be solved by the below method too
( 21, 9, 21, 11, 21, 13, 21_
21-12=9
9+12=21
21-10=11
11+10=21
21-8=13
13+8=21
21-6=15
This goes as -12+12,-10+10,-8+8,-6+6 where all digits get reduced by 2
( 21, 9, 21, 11, 21, 13, 21_
21-12=9
9+12=21
21-10=11
11+10=21
21-8=13
13+8=21
21-6=15
This goes as -12+12,-10+10,-8+8,-6+6 where all digits get reduced by 2
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