DKhanh

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9 Questions

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22	Prove that every year has at least one Friday the 13th
10	After swapping the positions of the hour and the minute hand, when will a clock still give a valid time?
9	Prove that all even integers $n \neq 2^k$ are expressible as a sum of consecutive positive integers
2	fill the board with dominos
1	How to find the minimum value of $\frac{x}{2x+3y}+\frac{y}{y+z}+\frac{z}{z+x}$?

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404 Reputation

+30	Prove that every year has at least one Friday the 13th
+25	Prove that all even integers $n \neq 2^k$ are expressible as a sum of consecutive positive integers
+5	How to find the minimum value of $\frac{x}{2x+3y}+\frac{y}{y+z}+\frac{z}{z+x}$?
+5	After swapping the positions of the hour and the minute hand, when will a clock still give a valid time?

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2 Answers

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1	How to “efficiently” compute the number of solution of $25x= 5y+8z$ such that $x,y,z \in [0,9]$ and $x,y,z \in \mathbb{W}$?
1	Maximizing the sum of two numbers, the sum of whose squares is constant

16 Tags

2 algebra-precalculus × 4	1 optimization
1 calculus × 3	0 puzzle × 2
1 elementary-number-theory × 2	0 number-theory × 2
1 inequality × 2	0 geometric-construction × 2
1 combinatorics	0 geometry × 2

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$Mathematics Stack Exchange$	Mathematics	404 rep	18
	Stack Overflow	164 rep	8
	Super User	123 rep	3

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