(1)27/1+272727/131313+272727/131313
=27/1+(27×10101)/(13×10101)+27×(10101)/(13×10101)
=27/1+27/13+27/13
=1
(2)1998又 1999/1998÷1998
=1998÷1998+1999/1998÷1998
=1+1999/1
=1又1999/1
(1)27/1+272727/131313+272727/131313
=27/1+(27×10101)/(13×10101)+27×(10101)/(13×10101)
=27/1+27/13+27/13
=1
(2)1998又 1999/1998÷1998
=1998÷1998+1999/1998÷1998
=1+1999/1
=1又1999/1