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saurabhmahajan: Master | Next Rank: 500 Posts; Posts: 250; Joined: Thu Jan 07, 2010 2:21 am; Thanked: 10 times

by saurabhmahajan » Sun Oct 17, 2010 10:34 pm

Hi Friends,

I am currently working on permutation and combination chapter. yesterday i was at the ATM and just thought how many combinations of my pin can be done IF no zero (0) should be there in my pin. I did the following way. Please check and let me know if i was right.

four numbers in pin which are repeatable.
so for first number 9 choices (1-9)
for second also 9 choices
for third also 9 choices
for fourth also 9 choices

so total combinations would be 9*9*9*9 = 6561
am i correct ?

Thanks and regards,
Saurabh Mahajan

I can understand you not winning,but i will not forgive you for not trying.

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Source: Beat The GMAT — Problem Solving | Sun Oct 17, 2010 10:34 pm

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Ian Stewart: GMAT Instructor; Posts: 2623; Joined: Mon Jun 02, 2008 3:17 amFollowed by: 355 members; Location: Montreal; Thanked: 1090 times; GMAT Score:780

by Ian Stewart » Sun Oct 17, 2010 11:03 pm

Yes, you are correct!

For online GMAT math tutoring, or to buy my higher-level Quant books and problem sets, contact me at ianstewartgmat at gmail.com

ianstewartgmat.com

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diebeatsthegmat: Legendary Member; Posts: 1119; Joined: Fri May 07, 2010 8:50 amFollowed by: 3 members; Thanked: 29 times

by diebeatsthegmat » Mon Oct 18, 2010 2:19 am

saurabhmahajan wrote:Hi Friends,

I am currently working on permutation and combination chapter. yesterday i was at the ATM and just thought how many combinations of my pin can be done IF no zero (0) should be there in my pin. I did the following way. Please check and let me know if i was right.

four numbers in pin which are repeatable.
so for first number 9 choices (1-9)
for second also 9 choices
for third also 9 choices
for fourth also 9 choices

so total combinations would be 9*9*9*9 = 6561
am i correct ?

wow... study everywhere....

nice

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