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

1. 

Look at this series: 2, 1, (1/2), (1/4), ... What number should come next?

[A]. (1/3)
[B]. (1/8)
[C]. (2/8)
[D]. (1/16)

Answer: Option B

Explanation:

This is a simple division series; each number is one-half of the previous number.

In other terms to say, the number is divided by 2 successively to get the next result.

4/2 = 2
2/2 = 1
1/2 = 1/2
(1/2)/2 = 1/4
(1/4)/2 = 1/8 and so on.


Payal said: (May 21, 2011)  
Thanks your explanation was really nice.

Parveen said: (May 24, 2011)  
I am bit confuse, regarding Reasoning. Get to how to do it all this, and about reasoning.

Deepa Singh said: (May 28, 2011)  
You can solve puzzle in news paper first you will confuse how can you solve but you try it again and again than you became in practice and you can solve it.

Upasana said: (May 29, 2011)  
Its a nice explanation.

Deepak said: (May 30, 2011)  
Definately it will helpful.

Abdul said: (Jun 3, 2011)  
Nicely Explained

Vengalarao said: (Jun 30, 2011)  
@deepa
Your explanation is very nice. Definately i will try to your concept.

Teja said: (Sep 15, 2011)  
Good explanation.

Lucky said: (Nov 6, 2011)  
Thanks for your explanation.

Rajpal Singh said: (Nov 25, 2011)  
Here why not multiple each no. By 2. Here first and second no. Multiple by 2 and third, fourth, . , . , . Not multiple by 2 its only divided by 2 why? while third no. Is same put.

Logical reasoning want same process in each no.

Jyoti Rawandhe said: (Jan 27, 2012)  
Thanks for giving this clear explanation...

Xduniya said: (Feb 8, 2012)  
Simply in every step we should deduct 1/2 to get the result.

For eg:.

1/4 - 1/2 = 1/8.

Sindhu said: (Apr 20, 2012)  
2/2=1,1/2,1/2/2=1/4,1/4/2=1/8

Deepa said: (Apr 26, 2012)  
4/2 = 2
2/2 = 1
1/2 = 1/2
(1/2)/2 = 1/4
(1/4)/2 = 1/8 and so on.

Subbu said: (May 10, 2012)  
My point of view it is solve simply half half the number we will write that's all.

Veeru said: (Jun 26, 2012)  
How can we estimate that we have consider first 4?

Because by dividing first number with 2 also we will get result.

Utharsh said: (Aug 15, 2012)  
Every time the denominator get doubled and the numerator rest with 1.

Umesh said: (Jan 5, 2013)  
Here if we multiply each number By 1/2 the we will get next number.

Akshay said: (Jan 29, 2013)  
1/8

From 1 to each number is divided by 2 than we get next number.

M.Ratnakar said: (Feb 6, 2013)  
How we got the logic can you explain detail.

4/2 = 2
2/2 = 1
1/2 = 1/2
(1/2)/2 = 1/4
(1/4)/2 = 1/8 and so on.

Lisa Price said: (Feb 11, 2013)  
I need help finding the next number in the series to:

1. 18,81,27,36,63?
2. 1/64,1/32,1/16,1/8,1/4,1/2?
3. 36,37,39,42,46,51?
4. 8,4,2,1,.5,.25,.25?
5. 2,4,6,5,7,9,8?
6. 154,77,81,78,39,43,40?
7. 1/2,1/4,1/3,1/6,1/5?
8. 2,3,4,8,9,10,20,21,22?
9. 2,5,14,41,122?
10. 15,18,54,57,171?
11. 18,81,27,72,36,63?
12. 1/64,1/32,1/16,1/8,1/4,1/2?
13. 36,37,39,42,46,51?
14. 2,4,6,5,7,9,8?
15. 154,77,81,78,39,43,40?

Vinod said: (Feb 20, 2013)  
Hey its very easy see.

2^1, 2^0, 2^-1, 2^-2, 2^-3

2^1=2
2^0=1
2^-1=(1/2)
2^-2=(1/4)
2^-3=(1/8)

Avinash Goyal said: (May 20, 2013)  
Every time the denominator get doubled and the numerator rest with 1.

Trinadh.K said: (Aug 5, 2013)  
@Lisa Price:

1. 18, 81, 27, 36, 63, 45, 54, 45....

2. 1/64, 1/32, 1/16, 1/8, 1/4, 1/2, 1, 2, 4... (you just multiply with 2).

3. 36, 37, 39, 42, 46, 51, 57, 64.. (+1 +2 +3 +4 +5 +6 +7).

Sravan Handsome said: (Oct 27, 2013)  
How we will expect first number is 4?

Sagar said: (Dec 2, 2013)  
I want to say that this series consist of successive powers of 2.

Haris said: (Feb 3, 2014)  
Nice but how can we expect this logic as first number is 4.

Himanshu said: (Feb 6, 2014)  
Just take a half of the number series.

1, 2 ...then,
2. 1/2 means 2/2 = 1;
3. 1/2 means 1/2/2 = 0.5/2 ( we can assume 1/2 as 0.5) = 1/4 and so on...

Naveen said: (May 11, 2014)  
5. 2, 4, 6, 5, 7, 9, 8, ?

Just add 2 up to 3 numbers and then subtract 1 from the third number.

2+2 = 4.
4+2= 6.
6-1 = 5.
5+2 = 7.
7+2 = 9.
9-1 = 8.
8+2 = 10.
10+2 = 12.

Surbhi Agrawal said: (May 11, 2014)  
Look at this:

2 - 1 = 1.
1 - 1/2 = 1/2.
1/2 - 1/4 = 1/4 .

Now,
1/4 - 1/8 = 1/8.
So answer is 1/8.

Kalyani said: (Jun 30, 2014)  
It is:

2^1 = 2.
2^0 = 1.
2^-1 = 1/2.
2^-2 = 1/4.
2^-3 = 1/8.

Kishor.B.C said: (Jul 5, 2014)  
Think logically you will get the answer.

Bipin said: (Sep 14, 2014)  
What is the no. series of the question.
3 , 34 , 192 , 782, ? , 1566

Venkatrao said: (Sep 22, 2014)  
Simple interest formulas and how to solve the problems.

Jitendra Sawwalakhe said: (Sep 30, 2014)  
we know that,the above no.decrease in order so,
2
1
1/2 = 0.5
1/4 = 0.25
1/8 = 0.125. So answer = 1/8.

Atif said: (Oct 14, 2014)  
I am not understand your all explanations about 1/2, 1/4 and 1/8.

Ragu said: (Dec 2, 2014)  
I am not understand your explanations about 1/8.

Amiya said: (Dec 19, 2014)  
Why first come 4/2 not other? I can't under stand.

Shahbaz Ahmad Naik said: (Jan 1, 2015)  
Sometimes the answers are very simple but due to unconfidancial we does not give it.

Shubhi said: (Jan 23, 2015)  
Very easy just half and divided by 2 like in:

Step 1: Take a no 4 itself.

4/2 = 2.

Step 2: After that half the number, so 4/2 = 2 and then divide by 2.

2/2 = 1.

Step 3:

1/2 = 1/2.
(1/2)/2 = 1/4.
(1/4)/2 = 1/8 and so on.

Jeevagan said: (Feb 27, 2015)  
It's not that big issue.!

First look at the series then start relating between them.

Ex:

Here in the series 2, 1, 1/2, 1/4,....

Just by first analysis we can conclude that next no. To 1st no is half time to it, and the logic is checked with next successive no.

Step 1:- 2,

Step 2:- 2, 1==>2, 2/2 (1),...

Step 3:- 2, 1, 1/2==>2, 2/2 (1) , 1/2 (1/2),....

Step 4:- 2, 1, 1/2, 1/4==>2, 2/2 (1), 1/2 (1/2) , (1/2) /2 (1/4),...

Papu said: (Mar 13, 2015)  
Answer can solve in this step 1/2*1/4*1/8*1/16 in this type.

Yanmar said: (Jul 12, 2015)  
1/3=1.
1/4=2.
1/5=3.
1/6=4 and so on.

Bank Po said: (Jul 28, 2015)  
Someone help me to find the next digit of the series 2, 6, 4, 12, 10.

Manisha said: (Sep 8, 2015)  
4*1/2 = 2.

2*1/2 = 1.

1*1/2 = 1/2.

1/2*1/2 = 1/4.

1/4*1/2 = 1/8.

Mostafiz said: (Sep 19, 2015)  
How does it possible?

Basavaraj said: (Sep 25, 2015)  
That's simple friends it is 1/8.

Jass Sukhana said: (Sep 26, 2015)  
Its very simple guys. Just need to be looking carefully.

Daniel said: (Oct 10, 2015)  
The series is geometric progression.

a2 divide by a1 so 1/2 and a3 by a2 so 1/2/1/1.

So the comment ratio is 1/2.

2, 1, 1/2, 1/4, 1/8.

Kifayet Hussain said: (Dec 16, 2015)  
Can any body explain it in a more better way please?

Naveen said: (Jan 6, 2016)  
2, 1, 1/2, 1/4, ?......2, 1, 0.5, 0.25.

See that series clearly know divided by 2, get next number.

So, 0.25/2 = 1/8.

Shubhendu Pathak said: (Feb 16, 2016)  
Suppose that it is 2, 1, (1/2), (1/4).

Than we can easily understand by doing this in this way.

Second number multiplied from first number and then get the next number.

Like: 1/2 * 1/4 = 1/8 solved.

Rakesh Kumar said: (Mar 30, 2016)  
Find the next number of the series : 8, 1/8, 22, 1/22, 37, 1/37, ?

Hardeepsinh said: (Jun 2, 2016)  
Excellent, and it's very helpful. Thank you all.

Ritika Singh said: (Jun 17, 2016)  
Its new concept for me but very helpful.

Shishir said: (Jun 23, 2016)  
Nice & logical explanation.

Santhosh said: (Jun 25, 2016)  
1 2 3.

4 5 ?

What comes in the question mark place?

Think logically.

And I'm saying it isn't 6.

Datacenters N R said: (Jul 3, 2016)  
These explanations are very helpful. Thank you all.

Epicram said: (Jul 8, 2016)  
Just Divide the next number by 2.

Shruthi said: (Jul 14, 2016)  
Please, (1/2) /2 how it comes 1/4?

Saiteja Hanumandla said: (Jul 16, 2016)  
According to the question.

Look at this series: 2, 1, (1/2) , (1/4) , . What number should come next?

Principle we need to follow this. This is a simple division series; each number is one-half of the previous number. 1 * 1/2 = 1/2.

2 * 1/2 = 2/2 =1.
1/4 * 1/2=1/8 so the answer is 1/8.

Let me know is there any mistake feel free to tell me because me also pure in maths.

Khushi Singla said: (Aug 3, 2016)  
Not able to get the explanation.

Sunil Rautels said: (Aug 9, 2016)  
It is 1/53 @Rakesh.

Hing Soo Beoy said: (Aug 13, 2016)  
1/4 - 1/2 = 1/8.

Raghunath said: (Aug 18, 2016)  
Thank you for all your explanations.

M.Raghuram Pgdm 1 said: (Aug 24, 2016)  
Half of the number taken as sequence so answer is 1/8.

Jhansi said: (Aug 24, 2016)  
Another logic of this sum is; Divide the given number by 2, then you will get the answer. Check it.

K.Sujitha said: (Aug 24, 2016)  
By dividing every number with 2 we can get the answer as 1/8.

Janmejaya Meher said: (Oct 13, 2016)  
Thank you for all your explanation.

Rajeswari said: (Oct 25, 2016)  
1/8 + 1/8 = 1/4,
1/4 + 1/4 = 1/2,
1/2 + 1/2 = 1,
1 + 1 = 2,
So, the answer is 1/8.

Vedant said: (Dec 9, 2016)  
Very very helpful. Thanks for all your explanation.

Shobha said: (Dec 12, 2016)  
Thank you all.

Shubham said: (Dec 25, 2016)  
Can anyone help me in finding the next number.

1) 4,9,10,21,22,39,34,57, ?
2) 15,105,315,693,1287, ?
3) 3,20,63,144, 275, ?

Sumeet said: (Dec 27, 2016)  
In simple 2^1, 2^0, 2^-1, 2^-2, 2^-3, ... and we get 2 ,1, (1/2), (1/4), (1/8) and so on.

Bhanu said: (Jan 10, 2017)  
It's very tough to identify the series. How to find it? Please give me the shortcut.

Julius said: (Feb 15, 2017)  
What is the meaning of this sign ^?

Please tell me correctly.

Pratheep said: (Mar 12, 2017)  
Really nice. Thanks for the given explanation.

Saran said: (Mar 23, 2017)  
I can't understand this. Give me the explanation clearly.

Ankit said: (May 9, 2017)  
Thank you for the given explanations.

Bhavana said: (May 10, 2017)  
Let the given series is A, B, C, D. If we divide D/C OR C/B OR B/A (in the order of the series, we get 1/2).

That shows A * 1/2 =B AND B * 1/2 = C.
SO,THE NEXT TERM IS D*1/2 = 1/4*1/2 = 1/8.

Santosh Goswami said: (Jun 10, 2017)  
I am not getting this, Please explain this.

Nitish Pandey said: (Jul 25, 2017)  
Am not getting it please explain.

Raju said: (Aug 30, 2017)  
Thank you all.

Arpita Roy said: (Feb 14, 2018)  
Thank you all for explaining it.

Arpita Roy said: (Feb 14, 2018)  
I am not getting this. Can anyone help me to get it?

Shiva said: (Mar 22, 2018)  
Thanks for explaining the answer.

Sravani said: (Mar 26, 2018)  
Nice explanation. Thanks all.

Ibraz Khan said: (May 24, 2018)  
@Shubham.

Keep taking the difference

15. 105, 315, 693, 1728, at last, you will get 48 common. By solving it we get the answer 2145.

Sandeep Kumar said: (Aug 25, 2018)  
Let me tell you.

As you know that term of geometric progression.
a/r, a, ar, ar2.
So if we write in this form ar, a, a/r, a/r2.
Where a =1 (Constant) and r=2 (Common Ratio).
i.e it can be written 2, 1, 1/2, 1/4, 1/8.

Sagarika Mahapatra said: (Oct 14, 2018)  
Nice explanations. Thanks all.

Mohan said: (Nov 1, 2018)  
Nice explanation, thanks.

Suryanarayan Mishra said: (Apr 1, 2019)  
Thanks all for explaining.

Amresh Sinha said: (Apr 5, 2019)  
Very nice explanation. Thanks all.

Sameer said: (May 25, 2019)  
Nice explanation. Thanks all.

Chandana said: (Jun 25, 2019)  
Thanks all for explaining.

Neha said: (Jul 13, 2019)  
Thanks all for your explanation it's very helpful for me.

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