# Mathematical Enigma - XX

If $a,b,c,d,e,f$ are positive real numbers which satisfy

$a+b+c+d+e+f=7,$

find the minimum value of

$\frac { 1 }{ a } +\frac { 4 }{ b } +\frac { 9 }{ c } +\frac { 16 }{ d } +\frac { 25 }{ e } +\frac { 36 }{ f } .$

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