Sorry, I was ambiguous. Fermat's little theorem says a^(p-1) mod p = 1 mod p, and a^p mod p = a. When p = 5, this means that any number raised to the 4th power is going to end in a 1 or a 6.
Euler's extension to Fermat's little theorem says that a^(t(n)+1) mod n = a mod n, where t(n) is a function. t(10) = 4, so this explains why the last digit of a number is unchanged after raising it to the fifth power.
t(100) = 40, so you'll find that after raising a number to the 41st power, the last two digits will be the same.
It's the fault of the Army Core of Engineers. The levees failed at much much less of their designed capacity. Despite citizens screaming about the problem, and suing the Core for a quadrillion dollars, nothing is being done about the issue and it's getting no media attention.
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Sorry, I was ambiguous. Fermat's little theorem says a^(p-1) mod p = 1 mod p, and a^p mod p = a. When p = 5, this means that any number raised to the 4th power is going to end in a 1 or a 6. Euler's extension to Fermat's little theorem says that a^(t(n)+1) mod n = a mod n, where t(n) is a function. t(10) = 4, so this explains why the last digit of a number is unchanged after raising it to the fifth power. t(100) = 40, so you'll find that after raising a number to the 41st power, the last two digits will be the same.
These tricks work for more than just base 10. You can prove it with Euler's generalization of Fermat's Little Theorem. http://en.wikipedia.org/wiki/Fermat's_little_theorem
Here's a nice documentary about the real problems behind the hurricanes.