Mathematics
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OpenStudy (lgbasallote):
How many 6 letter words can you create from the word ELEMENTARY?
Note: The words do not have to be legitimate
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OpenStudy (anonymous):
INFINATE!
OpenStudy (lgbasallote):
no...not really...there are finite letters
OpenStudy (anonymous):
ik
OpenStudy (anonymous):
36
OpenStudy (anonymous):
What haha
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OpenStudy (lgbasallote):
words
OpenStudy (lgbasallote):
yes exactly
OpenStudy (lgbasallote):
too bad you took it back though
OpenStudy (anonymous):
7C6 * 6! + 7C5 *6! + 7C4 * 6!/2! + 7C3 *6!/3!
OpenStudy (lgbasallote):
it's a pretty big number
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OpenStudy (lgbasallote):
sadly...no @sauravshakya
OpenStudy (zarkon):
do you know the answer?
OpenStudy (lgbasallote):
yes
OpenStudy (zarkon):
8015
OpenStudy (lgbasallote):
i don't think so...how did you get it? i may be wrong
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OpenStudy (zarkon):
\[_7P_6+ _7P_5+\frac{_7P_4}{2!}+\frac{_7P_3}{3!}\]
OpenStudy (zarkon):
I believe I am wrong now....give me a sec
OpenStudy (zarkon):
34650
OpenStudy (anonymous):
Can I ask a question?
OpenStudy (lgbasallote):
it's still too small...let me check
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OpenStudy (zarkon):
I should prob write this down instead of just typing on my calc :)
OpenStudy (lgbasallote):
hmm actually that was too big
OpenStudy (anonymous):
First tell me how many 6 letter words can u create from a,b,c,d,e,f
OpenStudy (lgbasallote):
that would be 6! yes?
OpenStudy (lgbasallote):
since none repeated
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OpenStudy (anonymous):
And how many 6 letter word from a,b,c,d,e,f,g
OpenStudy (zarkon):
now I'm getting sauravshakya answer...though I did it a different way
OpenStudy (anonymous):
Isnt it 7C6 *6!
OpenStudy (lgbasallote):
suppose so..yes
OpenStudy (anonymous):
Then what is wrong with my answer?
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OpenStudy (lgbasallote):
it's not the same as your example
OpenStudy (anonymous):
I took four cases with no e , 1 e , 2 e and 3e
OpenStudy (lgbasallote):
what did you do for no e?
OpenStudy (anonymous):
7C6*6!
OpenStudy (lgbasallote):
for 1 e?
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OpenStudy (anonymous):
7C5 *6!
OpenStudy (anonymous):
@lgbasallote ???
OpenStudy (zarkon):
36960 is correct (what sauravshakya got)
though I wrote it as
\[\sum_{x=0}^{3} {_7P_{6-x}}{6\choose x}\]
OpenStudy (anonymous):
It can also be 8C6 *6! + 8C5 *6!/2! + 8C4*6!/3!
OpenStudy (lgbasallote):
what about 2 e?
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OpenStudy (lgbasallote):
@sauravshakya
OpenStudy (anonymous):
7C4 * 6!/2!
OpenStudy (lgbasallote):
ahh we had different answers in the 2 e
OpenStudy (lgbasallote):
i think you should divide that by 4...
OpenStudy (zarkon):
>> A=perms([1 2 3 4 5 6 7 8 8 8]);
>> length(unique(A(:,1:6),'rows'))
ans = 36960
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OpenStudy (zarkon):
using octave
OpenStudy (lgbasallote):
wait...it seems i made a mistake in my solution...let me recheck
OpenStudy (lgbasallote):
yes. it's 46960
OpenStudy (lgbasallote):
36*
OpenStudy (zarkon):
octave would not lie ;)
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OpenStudy (lgbasallote):
a simpler looking solution though is \[7! + 6C1 \times 7P5 + 6C2 \times 7P4 + 6C3 \times 7P2\]
OpenStudy (zarkon):
you fix your 7P2 (make it 7P3) then you have the solution I gave above
OpenStudy (lgbasallote):
yeah should be 7P3