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Problem 569

Posted: Sun Sep 18, 2016 4:11 pm
by mctrafik
I worked this out by hand, but I can't seem to verify
"from the 9th mountain, he can see three peaks, those of the 5th, 7th and 8th mountain"

If, the mountain peaks were on a grid, then their coordinates would be :
9 - (430, 30)
8 - (328, 26)
7 - (238, 22)
5 - (100, 16)

The slope from 9th peak to 5th peak is (30 - 16) / (430 - 100) = 0.04242424242
But 9th to 8th peak is (30 - 26) / (430 - 328) = 0.03921568627

This means that 8th peak is blocking the view for 5th.

Re: Problem 569

Posted: Sun Sep 18, 2016 5:25 pm
by mpiotte
mctrafik wrote:...
If, the mountain peaks were on a grid, then their coordinates would be :
9 - (430, 30)
...
I would double check this value if I were you.

Re: Problem 569

Posted: Sun Sep 18, 2016 6:25 pm
by mctrafik
Ah yes. That one's off. Thank you. Funny thing is when making primes by hand... "49" isn't prime.