# find wrong term

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• May 24th 2008, 10:12 AM
neha1
find wrong term
find the wrong term in the given series
63,28,215,511
• May 24th 2008, 10:14 AM
earboth
Quote:

Originally Posted by hena
find the wrong term in the given series
63,28,215,511

How about 28 because it is the only even number?
• May 24th 2008, 10:14 AM
Moo
Hello,

Quote:

Originally Posted by hena
find the wrong term in the given series
63,28,215,511

Well, there are many possibilities...

- the numbers are odd, so 28 is the wrong term
- the numbers are in an increasing order, so 28 is the wrong term
- the sum of the numbers is <10, so 28 is the wrong term
- the one I prefer : they are all multiples of 7, so 215 is the wrong term :D

And another one :
- I don't know what term to choose, and I don't want to bother, so $\emptyset$ is the wrong term :p
• May 24th 2008, 10:27 AM
Isomorphism
Quote:

Originally Posted by hena
find the wrong term in the given series
63,28,215,511

Though I am pretty sure of my answer, I dont know why I am sure :P

The odd one out is 28 because the rest all are 1 short of a power of 2 :)
• May 24th 2008, 10:43 AM
earboth
Quote:

Originally Posted by Isomorphism
Though I am pretty sure of my answer, I dont know why I am sure :P

The odd one out is 28 because the rest all are 1 short of a power of 2 :)

Well, ähemm - isn't there is a slight difference between 215 and 255 :confused:
• May 24th 2008, 09:02 PM
Isomorphism
Quote:

Originally Posted by earboth
Well, ähemm - isn't there is a slight difference between 215 and 255 :confused:

(Lipssealed) (Crying) (Angry)
• May 25th 2008, 01:53 AM
Soroban
Hello, hena!

Quote:

Find the wrong term in the given sequence: 63, 28, 215, 511
Think cubes . . . $4^3 = 64,\quad 6^3 = 216,\quad 8^3 = 512$

We have: . $\begin{array}{cccc}
63 & 28 & 215 & 511 \\
\downarrow & \downarrow & \downarrow & \downarrow \\
4^3-1 & \quad{\color{red}?}\quad & 6^3-1 & 8^3-1 \end{array}$

The terms are of the form: $n^3-1$
. . except 28, which is $3^3 {\color{red}+} 1$ . . . and is in the wrong position.

• May 25th 2008, 07:46 PM
mr fantastic
Quote:

Originally Posted by neha1
find the wrong term in the given series
63,28,215,511

There's no wrong term. Furthermore, a possible fifth term is 803. Followed by 978, 923, 525, -329, .......