Forum location: QI.com Forum Index
> QI Games
View previous topic  View next topic
The New Number Fact Game 
Page 1 of 105 Goto page 1, 2, 3 ... 103, 104, 105 Next 
Sophie.A

629229. Sat Oct 24, 2009 4:44 pm 


1 is the only positive integer that is neither prime nor composite. 




principessa

629331. Sat Oct 24, 2009 10:59 pm 


2 is the only number whose factorial is prime 




cherrycoke

629339. Sun Oct 25, 2009 1:25 am 


3 is the resin identification code used in recycling to identify polyvinyl chloride.





Sophie.A

629346. Sun Oct 25, 2009 2:41 am 


Channel 4 was launched on 2 November 1983 with the programme “Countdown”. 




TheElephant

629356. Sun Oct 25, 2009 4:20 am 


5ive were rubbish. 




Sophie.A

629363. Sun Oct 25, 2009 4:45 am 


6 is the only number that is equal both to the sum of its positive factors smaller than itself (1+2+3) and and to the product of its positive factors smaller than itself (1×2×3).
Obviously a number is a product of its positive factors smaller than itself if and only if it is a product of exactly two distinct prime numbers. A number which is equal to the sum of its factors smaller than itself is called a perfect number. 6 is the only perfect number that is the product of exactly two distinct primes.[/list] Last edited by Sophie.A on Sun Nov 01, 2009 4:06 pm; edited 1 time in total





cherrycoke

629401. Sun Oct 25, 2009 6:20 am 


according to internet sources (Citation needed), seven ate nine 




Sophie.A

629413. Sun Oct 25, 2009 6:59 am 


8 is considered by the Chinese to be a lucky number. 




PDR

629415. Sun Oct 25, 2009 7:05 am 


In some european countries Nine is a refusenik in denial
PDR 




bemahan

629417. Sun Oct 25, 2009 7:10 am 


Quote:  1 x 9 + 2 = 11
12 x 9 + 3 = 111
123 x 9 + 4 = 1 111
1234 x 9 + 5 = 11 111
12345 x 9 + 6 = 111 111
123456 x 9 + 7 = 1 111 111
1234567 x 9 + 8 = 11 111 111
12345678 x 9 + 9 = 111 111 111
The results above are all triangular numbers in base9.

I'm not a mathematician but think stuff like this is magical. 




Sophie.A

629443. Sun Oct 25, 2009 8:21 am 


Observe that
12 = 1 + 11
123 = 1 + 11 + 111
1234 = 1 + 11 + 111 + 1111
12345 = 1 + 11 + 111 + 1111 + 11111
123456 = 1 + 11 + 111 + 1111 + 11111 + 111111
… etc
So
(11+1)×9 + 3 = (99 + 9) + 3 = (1001) + (101) + 3 = 100 + 10 + 1 = 111
(111+11+1)×9 + 4 = (999+99+9) + 4 = (10001) + (1001) + (101) + 4 = 1000 + 100 + 10 + 1 = 1111
… etc
Play around with these and you’re bound to find some interesting patterns (especially if you are familiar with the formula for the sum of terms of a geometric progression). Last edited by Sophie.A on Sun Oct 25, 2009 9:38 am; edited 4 times in total





Sophie.A

629444. Sun Oct 25, 2009 8:26 am 


To continue with the game …
10 = 1 + 2 + 3 + 4 




Vera C

629667. Mon Oct 26, 2009 5:37 am 


bemahan wrote:  I'm not a mathematician but think stuff like this is magical. 
Then maybe you'll might like this game.
(1) Think of a whole number, and square it.
(2) Multiply together the number before and the number after the resulting square.
(3) If the last digit of the new number is 4 or 9, add 3; if the last digit is not 4 or 9, add 2.
(4) Multiply by 20 and subtract 29.
The last two digits of the final number will always be: 11
Example:
(1) 27; 27^2 = 729
(2) 728 x 730 = 531440
(3) last digit not 4, so 531440 + 2 = 531442
(4) 531442 x 20 = 10628840; 10628840  29 = 106288411 Last edited by Vera C on Mon Oct 26, 2009 9:30 am; edited 1 time in total





Sophie.A

629686. Mon Oct 26, 2009 6:46 am 


(1) Think of a number other than 1 (any number except 1).
(2) Multiply by 3.
(3) Subtract 3.
(4) Multiply by 4.
(5) Divide by the number that is 1 less than than the original number you thought of.
The final answer is always 12. 




bemahan

629694. Mon Oct 26, 2009 7:07 am 


1/13 = 0.076923076923076923... (rational periodic infinite decimal)
On multiplying the periodic number 76923 by successive multiples of 13, this pattern is obtained:
76923 x 13 =0999999
76923 x 26 =1999998
76923 x 39 =2999997
76923 x 52 =3999996
76923 x 65 =4999995
76923 x 78 =5999994
76923 x 91 =6999993
76923 x 104 =7999992
76923 x 117 =8999991
76923 x 130 =9999990
Is it ok that I'm looking these up, or is that cheating? 




Page 1 of 105
Goto page 1, 2, 3 ... 103, 104, 105 Next
QI.com Forum Index > QI Games
All times are GMT  5 Hours
Search Forums
Powered by phpBB © 2001, 2002 phpBB Group