15/0.25 28.6*101-28.6 4.5/1.8*4.5/1.8 0.49/1.4 2.7/45 46*57+23*86【都用简便方法计算】

15/0.25
=(15*4)/(0.25*4)
=60/1
=60
28.6*101-28.6
=28.6*(101-1)
=28.6*100
=2860
4.5/1.8*4.5/1.8
=(45/18)^2
=(5/2)^2
=25/4
0.49/1.4
=(0.7*0.7)/(0.7*2)
=0.7/2
=7/20
2.7/45
=(0.3*9)/(5*9)
=0.3/5
=3/50
46*57+23*86
=23*2*57+23*86
=23*(114+86)
=23*200
=4600