This website contains problems from math contests. Problems and corresponding tags were obtained from the Art of Problem Solving website.

Tags were heavily modified to better represent problems.

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Found problems: 4

2010 Hanoi Open Mathematics Competitions, 3
Tags: digit , last , number theory
Find $5$ last digits of the number $M = 5^{2010}$ . (A): $65625$, (B): $45625$, (C): $25625$, (D): $15625$, (E) None of the above.

2014 Hanoi Open Mathematics Competitions, 3
Tags: number theory , last , digit
How many zeros are there in the last digits of the following number $P = 11\times12\times ...\times 88\times 89$ ? (A): $16$, (B): $17$, (C): $18$, (D): $19$, (E) None of the above.

2017 Hanoi Open Mathematics Competitions, 4
Tags: number theory , last , digit
Put $S = 2^1 + 3^5 + 4^9 + 5^{13} + ... + 505^{2013} + 506^{2017}$. The last digit of $S$ is (A): $1$ (B): $3$ (C): $5$ (D): $7$ (E): None of the above.

2013 Hanoi Open Mathematics Competitions, 4
Tags: number theory , last , digit
Let $A$ be an even number but not divisible by $10$. The last two digits of $A^{20}$ are: (A): $46$, (B): $56$, (C): $66$, (D): $76$, (E): None of the above.