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Hello and welcome to Seoul.
Here's today's math problem.
Last time I promised you something less tricky
with a little bit more math in it
So, here it is:
You take any number from 1 to 99.
If it's a one-digit number, let's say... 7
Then you just stop.
A one-digit number is a stop.
Or it's a two-digit number, let's say 25,
25 is a two-digit number
then here's what you do:
you multiply 2 by 5
and you get 10 which is again a two-digit number.
You multiply them again
and then you get 0.
0 is a one-digit number, so you stop.
And you get a chain of 1, 2, 3.
The length of this chain is 3.
One digit numbers make a chain which length is one, of course
Two-digit numbers can be...
Well, let's see 12.
It makes a chain that is 2. The length is 2.
So, here's the question:
Among the numbers from 1 to 99,
which one makes the longest chain?
Of course, you can try them all.
But what I want is another solution, something
a little bit more subtle than just trying them all.
So, find the right one,
and see you next time.
Bye!