Pleave help me find the next number...

Re: Pleave help me find the next number...


Hi,


189, I think ...


Grts,

Krekel

WHY?

Actually someone posted this answer already, it's not the right one:

a*n^3+b*n^2+c*n+d avec n=1,2,3 etc
a= -1/6
b=19/2
c=-19/3
d=4

for n =1 ------------ 7
n =2 ------------ 28
n=3 ------------ 66
n=4 ------------- 120
n=5 ------------- 189
n=6 ------------- 272 etc etc

Actually someone posted this answer already, it's not the right one:

a*n^3+b*n^2+c*n+d avec n=1,2,3 etc
a= -1/6
b=19/2
c=-19/3
d=4

for n =1 ------------ 7
n =2 ------------ 28
n=3 ------------ 66
n=4 ------------- 120
n=5 ------------- 189
n=6 ------------- 272 etc etc

The problem is, there are too many possible answers. Why did I say 189? Well, that's indeed kind of on loose screws (Dunglish?), since there are more than one possibilities ...


7, 28, 66, 120

(28-7), (66-28), (120-66) = 21, 38, 54

(38-21), (54-38) = 17, 16

17, 16 (next in line could be 15) so:

17, 16, 15 so:

21, 38, 54, 69 (54+15=69) so:

7, 28, 66, 120, 189 (120+69=189)


But, of course, maybe the sequence meant is: 17, 16, 17, 16 etc. Or maybe it's something completely different! You've only been given four numbers, that's (in this case) not enough to know what the meant sequence is.

Thanks loads, please post all your thoughts!

Thanks in advance! I'm desperate to solve this one!

Next in line, after 189, would indeed be 272, why is that wrong?

I don't know, I guess it's just not the right method they are asking for!

Well, tell 'them' that unspecified questions bring unclear answers.

OK I will post the 5th number in a minute and the one to find is the 6th

7...28...66...120....192

What's next?

Again, multiple answers are possible, but I think the number they want to hear is: 281 (next: 389)

But it could just as easily be: 279 (next: 387) ...

Can you expalin please?

Yes, sorry ...


7...28...66...120....192

(28-7)...(66-28)...(120-66)...(192-120) = 21...38...54...72




21...38...54...72

(38-21)...(54-38)...(72-54) = 17...16...18



So, the sequence here is probably 17...16...18...17...19...18...20 etc. (+2, -1, +2, -1, etc.)

But it could also be 17...16...18...15...19...14...20...13 (two sequences diverging by 1 every alternate step)

(thicker & blacker digits above are what we know for sure)


If it's the first, the next number is:

17...16...18...17... So:

21...38...54...72... (the new number here is: (72+17)) 89... Thus:

7...28...66...120...192... (the new number here is (192+89)) 281 ...

Thanks Krekel, you're clever,...

I'll let you know what the outcome is!

It's not the right one...sorry...

Hmmm, sorry to disappoint you then. Have you tried the diverging sequence too? The 17...16...18...15...19...14...20...13... ?

Which would mean: 7...28...66...120...192...279...387 ... ?

Yes I tried both...

I'm thinking about other options like:

squares of even numbers:

2^2 + 3

4^2 + 12

6^2 + 30

8^2 + 56

10^2 + 92

But I don't see any logic in the sequence 3, 12, 30, 56, 92

So:

12-3 ; 30-12 ; 56-30 ; 92-56 = 9 ; 18 ; 26 ; 36 (if only we had 27 they would all be multiples of 9 damn)


Same for squares of odds:

1^2 + 6

3^2 + 19

5^2 + 41

7^2 + 71

9^2 + 111

OK here's the 6th:

278

What's the 7th one?