26 replies to this topic

[rookie1ja]

Number Sequences - Back to the Number Puzzles
There are infinite formulas that will fit any finite series. Try to guess the following number in each sequence (using the most simple mathematical operations, because as I mentioned, there is more than one solution for each number sequence).

* 8723, 3872, 2387, ?
* 1, 4, 9, 18, 35, ?
* 23, 45, 89, 177, ?
* 7, 5, 8, 4, 9, 3, ?
* 11, 19, 14, 22, 17, 25, ?
* 3, 8, 15, 24, 35, ?
* 2, 4, 5, 10, 12, 24, 27, ?
* 1, 3, 4, 7, 11, 18, ?
* 99, 92, 86, 81, 77, ?
* 0, 4, 2, 6, 4, 8, ?
* 1, 2, 2, 4, 8, 11, 33, ?
* 1, 2, 6, 24, 120, ?
* 1, 2, 3, 6, 11, 20, 37, ?
* 5, 7, 12, 19, 31, 50, ?
* 27, 82, 41, 124, 62, 31, 94, 47, 142, 71, 214, 107, ?
* 126, 63, 190, 95, 286, 143, 430, 215, 646, 323, 970, ?
* 4, 7, 15, 29, 59, 117, ?
* 2, 3, 2, 3, 2, 4, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 4, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 4, 2, 3, 2, 3, 2, 5, ?
* 4, 4, 341, 6, 4, 4, 6, 6, 4, 4, 6, 10, 4, 4, 14, 6, 4, 4, 6, 6, 4, 4, 6, 22, 4, 4, 9, 6, ?

This old topic is locked since it was answered many times. You can check solution in the Spoiler below.
Pls visit New Puzzles section to see always fresh brain teasers.

Spoiler for Solution

Number Series - solution
• 8723, 3872, 2387, ? 7238 (moving of numerals)
• 1, 4, 9, 18, 35, ? 68 (x*2+2, +1, +0, -1, -2)
• 23, 45, 89, 177, ? 353 (x*2-1)
• 7, 5, 8, 4, 9, 3, ? 10, 2 (two series – every second number: 7, 8, 9, 10 and 5, 4, 3, 2)
• 11, 19, 14, 22, 17, 25, ? 20, 28 (two series – every second number: 11, 14, 17, 20 and 19, 22, 25, 28)
• 3, 8, 15, 24, 35, ? 48 (x+5, +7, +9, +11, +13)
• 2, 4, 5, 10, 12, 24, 27, ? 54, 58 (x*2, +1, *2, +2, *2, +3, *2, +4)
• 1, 3, 4, 7, 11, 18, ? 29 (a+b=c, b+c=d, c+d=e …)
• 99, 92, 86, 81, 77, ? 74 (x-7, -6, -5, -4, -3)
• 0, 4, 2, 6, 4, 8, ? 6 (x+4, -2, +4, -2, +4, -2)
• 1, 2, 2, 4, 8, 11, 33, ?
• 1, 2, 6, 24, 120, ? 720 (x*2, *3, *4, *5, *6)
• 1, 2, 3, 6, 11, 20, 37, ?
• 5, 7, 12, 19, 31, 50, ? 81 (a+b=c, b+c=d, c+d=e …)
• 27, 82, 41, 124, 62, 31, 94, 47, 142, 71, 214, 107, ? 322, 161 (x*3+1, /2, *3+1, /2 …)
• 126, 63, 190, 95, 286, 143, 430, 215, 646, 323, 970, ? 485, 1456 (x/2, *3+1, /2, *3+1 …)
• 4, 7, 15, 29, 59, 117, ? 235 (x*2-1, *2+1, *2-1 …)
• 2, 3, 2, 3, 2, 4, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 4, 2, 3, 2, 3, 2, 5, 2, 3, 2, 3, 2, 4, 2, 3, 2, 3, 2, 5, ? 2, 3, 2, 3, 2, 4, 2, 3, 2, 3, 2, 5
• 4, 4, 341, 6, 4, 4, 6, 6, 4, 4, 6, 10, 4, 4, 14, 6, 4, 4, 6, 6, 4, 4, 6, 22, 4, 4, 9, 6, ? 4, 4

[sn00bino]

• 1, 2, 2, 4, 8, 11, 33, ?

1 + 1 = 2
2 * 1 = 2
2 + 2 = 4
4 * 2 = 8
8 + 3 = 11
8 * 3 = 33
33 + 4 = 47
47 * 4 = 188
...

[chaos1133]

1, 2, 3, 6, 11, 20, 37, ?
i dont know about the change between 1 & 2 but
it is the # + the two previous numbers
2+1+0=3
3+2+1=6
6+3+2=11
11+6+3=20
20+11+6=37
37+20+11=68
?=68

[Baikin]

27, 82, 41, 124, 62, 31, 94, 47, 142, 71, 214, 107, ? 322, 161 (x*3+1, /2, *3+1, /2 …)

27 * 3 + 1 = 82
82 / 2 = 41
41 * 3 + 1 = 124
124 / 2 = 62
62 * 3 + 1 = 187

real formula should be:
Odd numbers: *3+1
Even numbers: /2

[iknowall]

1, 2, 3, 6, 11, 20, 37, ?
i dont know about the change between 1 & 2 but
it is the # + the two previous numbers
2+1+0=3
3+2+1=6
6+3+2=11
11+6+3=20
20+11+6=37
37+20+11=68
?=68

i think ur doing a version of the Fibonacci number which is 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55
it is x + # before it
so 0+1=1 1+1=2 2+1=3 ...

[imagoombah]

* 8723, 3872, 2387, ?
?=7238 (the numbers rotate positions one place to the right)

* 1, 4, 9, 18, 35, ?
?=? even the solution didn't make any sense, not sure what x represents

* 23, 45, 89, 177, ?
?=353 (double then subtract 1)

* 7, 5, 8, 4, 9, 3, ?
?=10 (subtract 2, add 3, subtract 4, add 5, subtract 6, add 7)

* 11, 19, 14, 22, 17, 25, ?
?=20 (add 8, subtract 5, add 8, subtract 5 etc.)

* 3, 8, 15, 24, 35, ?
?=48 (add the odd number 5, add the next odd number:7, add the next odd number:9 etc.)

* 2, 4, 5, 10, 12, 24, 27, ?
?=54 (multiply by 2, add 1, multiply by 2, add 2, multiply by 2, add 3, multiply by 2)

* 1, 3, 4, 7, 11, 18, ?
?=29 (add the previous two numbers together (with the exception of going from 1 to three where there is no previous number)

* 99, 92, 86, 81, 77, ?
?=74 (subtract 7, subtract 6, subtract 5, subtract 4, subtract 3)

* 0, 4, 2, 6, 4, 8, ?
?=6 (add four, subtract 2, add four, subtract 2 etc)

* 1, 2, 2, 4, 8, 11, 33, ?
?= sn00bino handled this one quite nicely

... and with that, I'm going to bed. I'll catch up on the rest later.

[imagoombah]

call me a nerd, I had to do one more

* 1, 2, 6, 24, 120, ?
?=720 (multiply the number by 1 then add it to itself, multiply the number by 2 then add it to itself, multiply the number by 3 then add it to itself, multiply the number by 4 then add it to itself, multiply the number by 5 then add it to itself)

[sindowg]

1,4,9,18,35,.....68
this was a reply I wrote down but cant remember how i got it, I jotted down 35+33=68 off to the side but I cant figure why.....hmmmm oh i got it 1 (2 spaces) 4 (4 spaces) 9 (8 spaces) 18 (16 spaces) 35 (32 spaces) 68 (64 spaces) 133 etc. etc.


23,45,89,177,.....303 23(+22) 45 (+44) 89(+88) 177(+176) 303(+352) 655 etc. etc.
I guess this proves there is more than one possible answer

[ahem cuba]

#02= (1, 4, 9, 18, 35,) 68, 133 (double previous solution quantity minus one: 3, 5, 9, 17, 33, 65)
#18= 2,3,2,3,2,4,2,3,2,3,2,5 (repetitive sequence)

sn00bino, you have 8*3=33 and 33+4=47 for #11? i think you meant:
8+3=11
11*3=33
33+4=37
37*4=148

Here's one for ya:
26, 25, 52, 50, 5, 4, 40, 39...?

[Slick_Rick9009]

* 1, 4, 9, 18, 35, ?
1*2+2=4
4*2+1=9
9*2+0=18
18*2+(-1)=35
35*2+(-2)=68
68*2+(-3)=133
133*2+(-4)=162
etc.

So you multiply by two and then add one less number each time starting by adding 2.