Multiply 9 with the first digit.
The flash mind reader works with multiples of 9, so all the multiples of 9 is the answer, from 9 to 81, but they are mixed up every time so as to confuse us.
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Do you mean 9x?
Number in tens place is xNumber in ones place is yThe number =10x+y10x+y-(x+y)=9xso the answer is always a multiple of 9
@Zun Kye Clear explanation :)5 points for group 4
If n = 8282=8x10+2=8a+2b10a+2b-(a+2b)=9aTherefore, the numbers is a multiple of 9
if you put 8x10+2=8a+2b, it will seem like a=10 and b=1 because 8x10+2=8x10(a)+2x1(b).
The answer will still be the same
@EthanThe 3rd line of the working, when generalized (using your example) would be 10a+bSo that it can represent any 2 digit number.
All answers are multiplication of 9 hence taking the number in tens as a and number in ones are b, 10a+b, subtract a+b=9a
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