脱式计算 ①163+20020÷70-70 ②1.56÷5.2×1.8÷0.12 ③10- ( 3 8 + 1 2 )÷ 3 8 ④6.8÷[(1.55+0.15)×50%].
①163+20020÷70-70, =163+286-70, =449-70, =379; ②1.56÷5.2×1.8÷0.12, =0.3×1.8÷0.12, =0.54÷0.12, =4.5; ③10- (
=10-
=10-
=7
④6.8÷[(1.55+0.15)×50%], =6.8÷[1.7×50%], =6.8÷0.85, =8. |