但我不懂,请大师讲解.

（252525×252252）／（525525×525252）
=[(25*10101)*(252*1001)]/[(525*1001)*(52*10101)]
=25*252/525*52
=25*252/(25*21)*52
=252/(21*52)
=(21*12)/(21*52)
=12/52
=3/13