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

11. 

Look at this series: 1.5, 2.3, 3.1, 3.9, ... What number should come next?

[A]. 4.2
[B]. 4.4
[C]. 4.7
[D]. 5.1

Answer: Option C

Explanation:

In this simple addition series, each number increases by 0.8.

Prathyusha said: (Feb 22, 2011)  
1.5+0.8=2.3
3.1+0.8=3.9
3.9+0.8=4.7
4.7 is answer

Krishna said: (Sep 25, 2011)  
1.5+1.6=3.1
3.1+1.6=4.7

Navya said: (Sep 27, 2011)  
2.3-1.5=0.8
3.1-2.3=0.8
3.9-3.1=0.8
4.7-3.9=0.8

Ram said: (Oct 20, 2011)  
2.3-1.5=0.8
3.1-2.3=0.8
3.9-3.1=0.8
4.7-3.9=0.8

Manish said: (Nov 22, 2011)  
2.3-1.5=0.8
3.1-2.3=0.8
3.9-3.1=0.8
4.7-3.9=0.8

Raji said: (Jan 31, 2012)  
2.3-1.5=0.8
3.1-2.3=0.8
3.9-3.1=0.8
x-3.9=0.8
x=0.8+3.9=4.7=ans.

Varun said: (Sep 7, 2012)  
We can make chain also. It is direct method.
3.1-1.5=1.6
3.1+1.6=4.7

Anu said: (Feb 26, 2013)  
Take the series as 15, 23, 31, 39...

Adding 8 to the previous number will give the next no.

15+8=23
23+8=31
31+8=39

So, 39+8= 47 for the series 15, 23, 31, 39..

And 4.7 for the series 1.5, 2.3, 3.1, 3.9...

Kartik Ahuja said: (May 9, 2014)  
Another solution is there.
Just add the digits of the individual number to once digit extent.

Like,
1+5, 2+3, 3+1, 3+9.

6, 5, 4, 3, now is 2 therefore option C is correct as 4+7=11 then 1+1=2 this complete the series.

Pawan Sharma said: (May 27, 2014)  
1.5+0.8 = 2.3.
3.1+0.8 = 3.9.
3.9+0.8 = 4.7.

Prasanth said: (Jun 19, 2014)  
Compare to all the answers ANU explanation is super and clear that can able to understand the dull students also.

Priyanka said: (Dec 30, 2014)  
2.3-1.5 = 0.8.
2.3+0.8 = 3.1.
3.1+0.8 = 3.9.
3.9+0.8 = 4.7.

Subhankar said: (Sep 30, 2015)  
Compare it carefully & you must find this.

Sandeep said: (Oct 6, 2015)  
2.3-1.5 = 0.8.
2.3+0.8 = 3.1.
3.1+0.8 = 3.9.
3.9+0.8 = 4.7.

Manthan (Jamla Gj 9 ) said: (Nov 4, 2015)  
15, 23, 31, 39, ?

31-15 = 16.
39-23 = 16.

So 31+16 = 47.

Alish said: (Jan 19, 2016)  
1.5+0.8 = 2.3,
2.3+0.8 = 3.1,
3.1+0.8 = 3.9,
3.9+0.8 = 4.7.

Answer: 4.7.

Roshan Roy said: (Mar 8, 2016)  
In this simple addition series, each number increases by 0.8.

Roshan Roy said: (Mar 9, 2016)  
The formula is +0.8 to the number in the question to get the sum :

1.5+0.8 = 2.3,
2.3+0.8 = 3.1,
3.1+0.8 = 3.9,
3.9+0.8 = 4.7.

Therefore the answer is 4.7.

Anusha said: (Apr 9, 2016)  
2.3 - 1.5 = 0.8.
3.1 - 2.3 = 0.8.
3.9 - 3.1 = 0.8.

x - 3.9 = 0.8 => x = 0.8 + 3.9 = 4.7

So answer is C.

Veerendra Devadiga said: (Apr 9, 2016)  
1.5 + 0.8 = 2.3.
2.3 + 0.8 = 3.1.
3.1 + 0.8 = 3.9.
3.9 + 0.8 = 4.7.

1.5, 2.3, 3.1, 3.9, 4.7.

Vinay said: (May 28, 2016)  
Yes, the answer is 4.7. Thank you all.

Vishalsaini said: (Jun 14, 2016)  
It's a good step for students and very helpful.

Urvam said: (Jul 13, 2016)  
We can also solve this question in such a way:

As in all terms, 1 is added to LHS digit and 2 is subtracted in RHS digit.

1 + 1 = 2 & 5 - 2 = 3 = 23.

As well as.

2 + 1 = 3 & 3 - 2 = 1 = 31.

M.Raghuram Pgdm 1 said: (Aug 24, 2016)  
Add by .8 so the answer is 4.7.

Hari Krishna said: (Oct 12, 2016)  
The logic is, Add 0.8 for each digit.

Jeya said: (Dec 13, 2016)  
1.5 + 0.8 = 2.3.
3.1 + 0.8 = 3.9.
3.9 + 0.8 = 4.7.

Dinesh said: (Feb 21, 2017)  
How 0.8 came?

Tell me the correct explanation.

Amit Soni said: (Apr 27, 2017)  
how 0.8 Came?

Please tell me, I wanted to know about this.

Jagannath Rout said: (May 16, 2017)  
2.3-1.5 = 0.8
3.1-2.3 = 0.8
3.9-3.1 = 0.8 (Just tell me about how acquire 4.7 this solution ) just addition 3.9+0.8 = 4.7
4.7-3.9 = 0.8.

Sruthi said: (May 22, 2017)  
It's a simple A.P with common difference .8.

So just add .8 to 3.9.
You get the answer 4.7.

Thameem Ansari said: (Nov 28, 2017)  
1.5+.8=2.3
2.3+.8=3.1
3.1+.8=3.9
3.9+.8=4.7 the difference is only no.8.so we can add 8 to the previous number.

Vishal Mittal said: (Jan 25, 2018)  
1.5, 2.3, 3.1, 3.9,.... Multiply this number by 10 15 23 31 39 ....

Take their difference which is 8
Then 39+8=47
Now divide it by 10 which gives answer 4.7.

Umesh Shettigar said: (May 8, 2018)  
2.3-1.5 = 0.8.
3.1-2.3 = 0.8.
3.9-3.1 = 0.8.
4.7-3.9 = 0.8.

Yogeeta said: (Jun 21, 2018)  
2.3-1.5 = 0.8.
3.1-2.3 = 0.8.
3.9-3.1 = 0.8.
4.7-3.9 = 0.8.

Manjariu said: (Nov 17, 2018)  
1.5 + 0.8 = 2.3,
2.3 + 0.8 = 3.1,
3.1 + 0.8 = 3.9,
3.9 + 0.8 = 4.7.

Vicky Kumar Sharma said: (Mar 20, 2019)  
1.5 + 0.8 = 2.3,
2.3 + 0.8 = 3.1,
3.1 + 0.8 = 3.9,
3.9 + 0.8 = 4.7.

Mansi Sharma said: (May 20, 2019)  
In this series, it is increases by 0.8.

Foram said: (Aug 16, 2019)  
Assume that there is no (.) in the series,
15 , 23 , 31 , 39
+8 +8 +8

Add 8 in the next numbers,
So, adding +8 in the 39 the answer will be 47.

And finally, the answer is 4.7.

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