下面的简便方法算,最后一题不用.
1个回答

①:(1/2-1/3)X3/4除1/4

=(1/2-1/3)×3/4×4

=(1/2-1/3)×3

=3/2-1= 1/2

②:35×25%+1/4×27+38除4

=35×1/4+1/4×27+38×1/4

=1/4×(35+27+38)

=25

③:28.8-640%-2.8-4.6

=28.8-2.8-64-4.6

=26-64-4.6

=-42.6

④:(15-5)X5/13+8/15X10

=10×5/13+8/15×10

=10×(5/13+8/15) 这个地方是不是错了?8/15可能是8/13?

=358/39

⑤:x:0.42=2/3

x=0.28