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?
14
15
21
23
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 3 of 5.

A.G RAO said:   10 years ago
The 21 is a referendums numbers every one should be show:

9+2 = 11, 11+2 = 13, 13+2 = 15.

So 15 is right answers nor essay answer.

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?

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.
(1)

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).

Rohan said:   1 decade ago
Can anyone solve this Equation?

2(L+B) = 180 -------------- 1.

L - B = 8 -------------- 2.

Find the value of L and B?

Manoj said:   1 decade ago
21, 9, 21, 11, 21, 13.

21-----after 9, 11, 13.

13-11=2, 11-9=2.

Series on 2.

Then 13+2=15 answer.

Boga laxman said:   1 decade ago
21-9 = 12
9-21 = 12
21-11 = 10
11-21 = 10
21-13 = 8
13-21 = 8
21-15 = 6

So answer is 15.

Bhargavi said:   1 decade ago
In increasing order by adding +2 then,
9+2 = 11.
11+2 = 13.
13+2 = 15.

So answer is 15.

Preeti said:   1 decade ago
9 +2 = 11.
11+2 = 13.
13+2 = 15.

Pawan Sharma said:   1 decade ago
21-12 = 9.
21-10 = 11.
21-8 = 13.
21-6 = 15.


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