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 1 of 5.
Nitish said:
1 decade ago
Here in this series 21 is not interchanged after one one numbers like 9, 11 and 13.
So let's throw out the number 21.
So, now we can easily get the answer. In 9 the number 2 is added to get 11.
In 11 the number 2 is added again to get 13. And finally we get the series is on 2.
So we need to add 2 in 13, 2+13=15 (ANS).
So let's throw out the number 21.
So, now we can easily get the answer. In 9 the number 2 is added to get 11.
In 11 the number 2 is added again to get 13. And finally we get the series is on 2.
So we need to add 2 in 13, 2+13=15 (ANS).
Priyangsi said:
1 decade ago
ANS to you Rohan,
Given:
2(L+B) = 180.
= L+B = 180/2 = 90----------- 1.
And we have,
L-B = 8------------ 2.
On adding 1 and 2, we get,
= L+B+L-B = 90+8.
= 2L = 98.
= L = 98/2 = 49 (value of L).
And B = L-8 (From 2).
B = 49-8 = 41 (value of B).
So, answer => L = 49.
=> B = 41.
Given:
2(L+B) = 180.
= L+B = 180/2 = 90----------- 1.
And we have,
L-B = 8------------ 2.
On adding 1 and 2, we get,
= L+B+L-B = 90+8.
= 2L = 98.
= L = 98/2 = 49 (value of L).
And B = L-8 (From 2).
B = 49-8 = 41 (value of B).
So, answer => L = 49.
=> B = 41.
(1)
Malkeet singh said:
1 decade ago
Another method:
21 is coming after every different number.
If we add 2 with every different number in ascending order automatic give the result.
For example:
different no. 9+2=11
different no. 11+2=13
different no. 13+2=15 and so on.
21 is coming after every different number.
If we add 2 with every different number in ascending order automatic give the result.
For example:
different no. 9+2=11
different no. 11+2=13
different no. 13+2=15 and so on.
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
Rajini arunkumar said:
8 years ago
21-12 = 9
9+12 = 21
21-10 = 11
11+10 = 21
21-8 = 13
13+8 = 21
21-6 = 15.
Why substracting 6 means, they subtracting adding like 10,8 so next even no.is 6 only.
9+12 = 21
21-10 = 11
11+10 = 21
21-8 = 13
13+8 = 21
21-6 = 15.
Why substracting 6 means, they subtracting adding like 10,8 so next even no.is 6 only.
(1)
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.
Shivam said:
9 years ago
You see that the series is,
21 - 9 = 12.
Again after 9 have 21.
Again you see 2,
And again 21 - 9.
You see that 10, 10, 8, 8, 6, 6 series has follows.
21 - 9 = 12.
Again after 9 have 21.
Again you see 2,
And again 21 - 9.
You see that 10, 10, 8, 8, 6, 6 series has follows.
Vivek srivastava said:
1 decade ago
It is difference of number are 2
so
21-9=12
21-11=10
21-13=8
and
12-2=10
10-2=8
8-2=6
so
21-6=15
This is the right answer solved by vivek Srivastava.
so
21-9=12
21-11=10
21-13=8
and
12-2=10
10-2=8
8-2=6
so
21-6=15
This is the right answer solved by vivek Srivastava.
CHINNA...IIIT said:
1 decade ago
*It is done in another way i.e..
by using decreasing order
21-12=9
21-10=11
21-8=13
21-6=15
so, decrease the subtract number to one by one..2
by using decreasing order
21-12=9
21-10=11
21-8=13
21-6=15
so, decrease the subtract number to one by one..2
(3)
Meera said:
10 years ago
How to find the relationship between the first two numbers which bears the same relation between the third number as the first two bears?
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