Aptitude - Odd Man Out and Series - Discussion

Find out the wrong number in the given sequence of numbers.

13. 

36, 54, 18, 27, 9, 18.5, 4.5

[A]. 4.5
[B]. 18.5
[C]. 54
[D]. 18

Answer: Option B

Explanation:

The terms are alternatively multiplied by 1.5 and divided by 3. However, 18.5 does not satisfy it.

Karthik said: (Jul 6, 2010)  
The given terms are exactly divisible by 3 except 18.5
Hence the answer is 18.5

Hrushikesh said: (Aug 9, 2010)  
The given terms are divisible by 3 and 9 except 18.5

Udayakumar said: (Dec 27, 2010)  
The diff b/w 54&36 is 18.the next no is 18. 27&18 is 9.the next no is 9. so in place of 18.5 if 13.5 comes then the diff is 4.5 which is the next no. so 18.5 is the wrong no

Kamaljeet said: (Feb 9, 2011)  
Great work udaya.

Riby said: (Mar 30, 2011)  
This is a truly fantastic explanation udayakumar.

Mathan said: (May 5, 2011)  
The digits are in the odd places from the right corner is multiplied by 2.as it in the even places the 6th place no should be 13.5(18.5) when multiplied by 2 is 27.

Pranesh said: (May 18, 2011)  
Alternative number is divisible by 2.

Ashik Mohammed Nazar said: (Jun 7, 2011)  
All the others except 18.5 are divisible by 4.5

Nagendramurthy said: (Jun 17, 2011)  
For this we have 3 to 4 alternative ways

1st all divisible 9 except 18.5
2nd all divisible 4.5 except 18.5
3rd sum of no is 9 ..

that is
54 (5+4=9)
36 (3+6=9)
27 (2+7=9)
4.5 also (4+5=9)
except 18.5 (1+8+5=14)

4th method is what udayakumar told.. great work udayakumar..

Sravya said: (Aug 3, 2011)  
Simply we can say that

36+18=54
18+9=27
9+4.5=13.5
by this we can say 18.5 is wrong

Kiran said: (Aug 29, 2011)  
Pick alternate numbers

4.5*2=9
9*2=18
18*2=36

In the same way 18.5 is not the begining one for 2nd series. so ans 18.5.

Farhat said: (Sep 7, 2011)  
Nice question.

Guru Prakash.C said: (Nov 9, 2011)  
The difference of first two is the third number

Akansh said: (Dec 17, 2011)  
Just divide all term by 9 except 18.5 all will be divided ;).

Subha said: (Feb 2, 2012)  
36/2=18
54/2=27
18/2=9
27/2=13.5
9/2=4.5
so 18.5 is wrong

Tarun said: (Dec 20, 2012)  
Two series both are divided by 2 in order to get the next term...
36/2=18
18/2=9
9/2=4.5
.....
and
54/2=27
27/2=13.5
13.5/2=6.75
....

Vinoth said: (Jul 31, 2013)  
Take the odd series first.

36/2 = 18.
18/2 = 9.
9/2 = 4.5.

Take the even series.

54/2 = 27.
27/2 = 13.5 but here 18.5.

So 18.5 is the wrong number in the series.

Meenali said: (Aug 14, 2013)  
Sum of digits is 9 in all the numbers. Odd one is that which does not satisfy this condition.

Raju said: (Mar 8, 2014)  
Divide all numbers with 2 and relate them alternatively hence 18.5 is wrong.

Nivedha said: (Jan 21, 2015)  
Divide the terms by 2 to get the alternative number.

36/2 = 18.
18/2 = 9.
9/2 = 4.5 and 54/2 = 27.
27/2 = 13.5.

So 18.5 is incorrect.

Roniee said: (Jul 22, 2015)  
I read it as whatever was being added to it, the double of it was deducted from it so according to me 18 added 36 deducted 9 added 18 deducted therefore when 9.5 was added 19 should have been deducted & 4.5 would be wrong & -0.5 could be the answer instead of 4.5 & I conclude that I considered 4.5 wrong!

T Dogg said: (Jul 30, 2015)  
I just don't get it ! Maybe I have an IQ.

I answered 4.5. All the other numbers individually add up to '9'.

Krishnamoorthy said: (May 23, 2016)  
@Nivedha.

Your answer is exactly correct and simple. Thankyou.

Prakash said: (Aug 17, 2016)  
Agree @Nagendramurthy.

(5 + 4) = 9
(3 + 6) = 9
(2 + 7) = 9
(1 + 8 + 5) = 14

Devendra said: (Aug 26, 2016)  
Forget the decimal point then every number sums up 9 except 18.5 so it is wrong.

Amol Sathewad said: (Oct 12, 2016)  
54 - 36 = 18 next no.
27 - 18 = 9 next no.
13.5 - 9 = 4.5 next no.
So 18.5 wrong.

Anshu Tiwari said: (Jan 12, 2017)  
Every term will be divisible by 9 except 18.5.
So 18.5 is wrong.

Anjali Mittal said: (Sep 27, 2017)  
1 and 2 number is the multiple of 3rd number and so on, but 18. 5 doesn't satisfy this condition i.e (18, 18*2=36, 18*3=54) (9, 9*2=18, 9*3=27) (4.5, 4.5*2=9, 4. 5*3=13.5). There should be 13.5 instead of 18.5.

Mohammed Abu Aslam said: (Nov 7, 2017)  
All the numbers in the table are multiples of 4.5 i.e( all the terms in the table satisfy the table of 4.5 except 18.5).

Hence the answer is 18.5.

Prem Malde said: (Dec 6, 2017)  
18.5 cannot be divided by 9 while others can be divided by 9.

So answer is 18.5.

Pichi Viany said: (Dec 12, 2017)  
Nice explanations. Thanks all.

Elakkiya said: (Jun 14, 2018)  
@All.

In my view,

I took the alternate numbers in one series.
4.5,9,18,36.

4.5*2=9*2=18*2=36,
13.5*2=27*2=54,
So 18.5 is wrong I think.

Sudhakar Kr said: (Aug 7, 2018)  
We may solve in another method tooo.

Consider odd series 36,18,9,4.5 (÷2).
Consider even series 54,27,13.5(÷2).
Wrong one is 18.5.

Harsh said: (Jan 5, 2019)  
Numbers are 36, 54, 18, 27, 9, 18.5, 4.5.


4.5+4.5=9,
18.5+18.5=37,
9+9=18,
27+27=54,
18+18=36,

Here, only the addition of 18.5 is not obtained. So, the answer is B.

Mandal said: (Oct 8, 2019)  
The simplest way is for all the numbers the sum of all the digits is 9 (36 is 3+6=9, 54 is 5+4=9, 27 is 2+7=9, 9 is 9, 4.5 is 4+5=9).

But for 18.5 its 1+8+5=14 and thus not equal to 9.

I am not sure if its a correct solution or not but this is the way that I could think of.

Turubilli Hema Lata said: (May 3, 2021)  
Solution:
36-->3+6 = 9
54-->5+4 = 9
18-->1+8 = 9
27-->2+7 = 9
9 will write as 09-->0+9 = 9
18.5--->1+8+5 = 14
4.5-->4+5 = 9.

All are divisible by 3 except 18.5 so answer is 18.5(B).

Abi said: (Jun 12, 2021)  
No @Udhaya.

54 - 36 = 18,
27 - 18 = 9.

18.5 - 9 is not equal to 4.5.
So he said 18.5 is wrong.

My opinion is why we change 18.5, we also change 9..So 9 is also wrong.

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