Question

Express 2.12345......... in p/q form

Answer 1

if there is a bar on 12345 then the p/q form can be written 
let x be the ratio
x=2.12345 bar on it (1)    (remeber bar is only on 12345)

multiply both sides by 100000
100000x=212345.12345 bar on it(2)

substract equation(1) from equation(2)
 100000x=212345.12345 bar on it
-           x=2.12345 bar on it
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   99999x=212343
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x=212343/99999
this is the rationalised form of 2.12345 bar on it

and if there is no bar it can't be written in p/q form