How many 9's between 1-100?

SandEagle

Lifer
Aug 4, 2007
16,809
13
0
gah, i had to redo this many times... try figuring it out without writing anything down.

 

Chaotic42

Lifer
Jun 15, 2001
34,348
1,523
126
10 for each number which ends in 9
9 more for each number which begins with 9

I'm going with 19.
 

Poulsonator

Golden Member
Aug 19, 2002
1,597
0
76
Originally posted by: Chaotic42
Originally posted by: SandEagle
wrong :)

Well, it is Sunday night so

09
19
29
39
49
59
69
79
89
99

90
91
92
93
94
95
96
97
98

What am I missing here?

You're missing a key part of the question. How many 9's are there inbetween 1-100?

It's 20 as you forgot to count the nine that begins 99.
 

Chaotic42

Lifer
Jun 15, 2001
34,348
1,523
126
Originally posted by: Poulsonator
You're missing a key part of the question. How many 9's are there inbetween 1-100?

It's 20 as you forgot to count the nine that begins 99.

Yup. It's 20 as long as he's talking integers.
 

DrPizza

Administrator Elite Member Goat Whisperer
Mar 5, 2001
49,601
167
111
www.slatebrookfarm.com
Forget about 100 for a moment, and write the units as 01, 02, etc., and start with 00.
So, 00 to 99
100 numbers, each two digits each, for a total of 200 digits.
Each digit occurs with the same frequency, so 1/10th of the 200 digits are 9's.

20



While my method may seem a little harder at first, here's a followup question: how many 7's are there between 1 and 1 billion?
(suddenly, you see the wisdom in DrPizza)


Also, SandEagle, this is the easiest method to do without writing anything down. I think that most people who did it in their head wouldn't have counted two 9's for the number 99. Of course, there are 10 numbers that end in 9, and 10 two-digit numbers that begin with 9. So, that's 20.
 

TruePaige

Diamond Member
Oct 22, 2006
9,874
2
0
Every number from 9 up contains 9 units, so I'll say you could also argue for 92.

100-91 = 9
99-90 = 9

etc.. ;)
 

her209

No Lifer
Oct 11, 2000
56,336
11
0
Technically, there are an infinite number of 9s between 0-100 because each number can be represented as a fraction.
 
Sep 29, 2004
18,656
67
91
Holy crap, I read over the responses. WE are all idiots. Please lock thread. PLEASE! IS this really a good use of brain power? I jsut sent hte weekend reading the CMT annual reports.
 

Nik

Lifer
Jun 5, 2006
16,101
2
56
Originally posted by: pontifex
0.

I don't see any 9s between "1-100"

In the English language, there would be an infinite number of 9's between all numbers on the number line between 1 and 100.

In the English language, there would be no 9's on the number line among 1 and 100.

If the question is how many 9's are used to make any whole number between 1-100, the answer is 20. If the answer is how many times the number 9 appears between 1-100, the answer is once.
 

DrPizza

Administrator Elite Member Goat Whisperer
Mar 5, 2001
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www.slatebrookfarm.com
Originally posted by: TruePaige
Every number from 9 up contains 9 units, so I'll say you could also argue for 92.

100-91 = 9
99-90 = 9

etc.. ;)

I think you'd lose the argument for 92. I think you mean a much larger number, because using your argument, the number 90 contains ten 9's.

Off the top of my head, I believe that's 496 nines.

 

DrPizza

Administrator Elite Member Goat Whisperer
Mar 5, 2001
49,601
167
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www.slatebrookfarm.com
Originally posted by: Nik
Originally posted by: pontifex
0.

I don't see any 9s between "1-100"

In the English language, there would be an infinite number of 9's between all numbers on the number line between 1 and 100.

In the English language, there would be no 9's on the number line among 1 and 100.

If the question is how many 9's are used to make any whole number between 1-100, the answer is 19.As pointed out in the thread, 20. You fail. If the answer is how many times the number 9 appears between 1-100, the answer is once.