Shoutbox

sorry that should have been 4 letters .... a,b,c,d and e
viz. = namely ....
Its not probability .... its using permutation and combination

quote:

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Originally posted by CookieRevised
To calculate the equivalent base ten number:
= 0 * 5^4   +   3 * 5^3   +   1 * 5^2   +   2 * 5^1   +   0 * 5^0
= 410

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quote:

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Originally posted by John Anderton
The answer i worked out is 216

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I dunno that formula that u r using .... can u do the same question with permutation and combination ..... i have used a simple logic .... i hope u understand ... her it goes.
1st word aaaaa
2nd         aaaab
3             aaaac
4             aaaad
5             aaaba

Ok so 4 changes r possible in the 1st letter (from the right) (like units place in numbers) ....
5th change will make the 2nd letter from the right change once.
So When the 1st letter changes 25 times (5*5) then the 3rd letter from the right will change.
When the 1st letter changes 125 times then the 4th letter changes once .....
the 4th letter from the right changes 3 times (a -> b -> c ->d) thus ..... 125*3 = 375

Now the 3rd letter from the right needs to change 1 time (a -> b) so ..... so the 1st letter needs to change 25 times .... {Total of 375 + 25 = 400 words have passed}

Now the 2nd letter from the left needs to change 2 times (a -> b -> c) so the 1st letter needs to change 5 * 2 = 10 times {so a total of 410 words have passed and we have reached adbca}

So shouldnt that be the answer
... our ans are almost the same but urs is 411 .
Where did i go wrong
I started my counting from one

The earlier ans i got was different as i had taken the factor as 4 ie. for every 4 changes of the 1st letter the next one changes once.