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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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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

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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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