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Last digits of a huge power of eleven mod 50

Question

What remainder does 11236011^{2360} leave on division by 5050?

Short answer

11. By the binomial theorem 115=(10+1)5=1+50+(multiples of 100)11^5=(10+1)^5=1+50+(\text{multiples of }100), so 115≡1(mod50)11^5\equiv1\pmod{50}. Since 2360=5⋅4722360=5\cdot472, 112360=(115)472≡111^{2360}=(11^5)^{472}\equiv1.

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