gregers Posted February 5, 2009 Report Posted February 5, 2009 must be magic.or logic.http://www.murderousmaths.co.uk/games/mindreader/index.htm Quote
insider Posted February 9, 2009 Report Posted February 9, 2009 Simple maths if you remember your algebra! a = 1st digit (tens), b = 2nd digit (units). So in their example, a=2 and b=8. Choose a random two digit number (e.g. 28). [ 10a + b ]Add the two digits (2+8=10). [ a + b ]Subtract the result from the number (28-10=18). [ 10a + b - ( a + b ) = 9a ] The answer is always 9 times the first digit. The pictures on the second page are the same for all multiples of 9 (9, 18, 27, etc.) Quote
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