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> Logic (1)> Probability> Shapes> General
> Numbers (1)> Games> Paradoxes> Riddles
> Just Math (1)> Science> Algorithms
You have 101 coins, and you know that 50 of them are counterfeit.
Every true coin has the same weight, an unknown integer, and every false coin has the same weight, which differs from that of a true coin by 1 gram.
You also have a two-pan pointer scale that will show you the difference in weight between the contents of each pan.

You randomly oick up a coin.
Find in a single weighing whether it’s true or false.

Source:Sergei Aleksandrovich Genkin, Dmitrii Vladimirovich Fomin, and Ilia Itenberg, Mathematical Circles: (Russian Experience), 1996.)
(No Solution Yet, 1 Comments) Submitted on 2018-10-22 by Ady TZIDON   
Difficulty: 2 of 5 Bonus: Very Magic Square (in Numbers) Rating: 3.33
Can you create a 4x4 magic square that still works with the same total when turned upside down?

[A Magic Square is a grid of numbers whose rows, columns and long diagonals add up to the same total. All the numbers in the square must be different.]

[By 'turned upside down' I mean that if 106 is the number in the top left corner in the original magic square, then 901 is in the bottom right corner of the inverted square]
(Solution Posted, 9 Comments) Submitted on 2003-11-21 by fwaff   
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Recently Posted Solutions:
Difficulty: 3 of 5Get the bases! (in Just Math)
Submitted By Ady TZIDON. Solution posted on 2018-10-18 02:24:50
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