6but for doin quesns similar to this it 'lll be better if there is a formal proof....
Find least no. of digits in x ,
When f(f(f(f(x)))) = 1
whre f(x) is the sum of the digits in x
x > f(x)
f(x) > f(f(x))
f(f(x)) > f(f(f(x))) > 1
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3 Answers
62f(f(f(x))) has to be 10
if f(f(f(x))) = 10 then f(f(x)) = 19
then f(x) can be 199
so x has to have 23 digits..
the smallest x being.. 199999999999999 (22 9's)
This is far from a formal proof.. but more like a guess work..
neone for a formal and correct proof?
1Thnx a lot dude.....
U rokk
I dont need a formal proof
This is gud enuf..
Thanx a lot
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