GMAT Changed on April 16th - Read about the latest changes here

 It is currently 22 Apr 2018, 13:04

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# Counting all 2-distinct-digit occurrences from 4-digits combinations

Author Message
Intern
Joined: 02 Nov 2017
Posts: 1
Counting all 2-distinct-digit occurrences from 4-digits combinations [#permalink]

### Show Tags

02 Nov 2017, 11:13
1
This post was
BOOKMARKED
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions

### HideShow timer Statistics

Currently I'm facing a problem to find out the formula to count 2 distinct digits say X and Y from a 4-digit combinations, where each digit can be range from 0 to 9, programming solution give me an answer of 974

I'm able to find out if to count 1 digit say X from a 4-digit combinations: $$10^4 - 9^4 = 1000 - 6561 = 3439$$

I've tried to read some articles, but a bit too dumb to understand how it works. I'm trying to get my colleague help too, it seem not so easy to get the formula, also not sure the programming answer is correct.

--== Message from GMAT Club Team ==--

This is not a quality discussion. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.
Math Expert
Joined: 02 Sep 2009
Posts: 44599
Re: Counting all 2-distinct-digit occurrences from 4-digits combinations [#permalink]

### Show Tags

02 Nov 2017, 23:35
whislai wrote:
Currently I'm facing a problem to find out the formula to count 2 distinct digits say X and Y from a 4-digit combinations, where each digit can be range from 0 to 9, programming solution give me an answer of 974

I'm able to find out if to count 1 digit say X from a 4-digit combinations: $$10^4 - 9^4 = 1000 - 6561 = 3439$$

I've tried to read some articles, but a bit too dumb to understand how it works. I'm trying to get my colleague help too, it seem not so easy to get the formula, also not sure the programming answer is correct.

--== Message from GMAT Club Team ==--

This is not a quality discussion. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.

_________________
Re: Counting all 2-distinct-digit occurrences from 4-digits combinations   [#permalink] 02 Nov 2017, 23:35
Display posts from previous: Sort by