①-(+) ②+×
① - +
② -( - )
③ + +
④8.11- +2.89-
400÷80= 7.7+2.3= 4.2÷0.6= 1﹣0.91=
0.04×1000= 10÷1.25×9= 24×0.25= 23﹣1=
+= ×20=
9×3.14= +÷= 36×= 728﹣299=
72÷0.4= 75×10%= 1÷×= 12.56÷6.28=