1、△+☆=☆+△ ( )

2、a ╳ b = b ╳ a ( )

3、(43 ╳ 25 ) ╳ 8=43╳ (25 ╳ 8) ( )

4、△+□+☆ = △+(□+☆) ( )

5、0 ╳ b = b ╳ 0 ( )

五、计算题。(共25分)

1、直接写出得数。(5分)

25 ╳ 4 = 48 + 52 = 5 ╳ 14 = 73 + 27 =

40 ╳ 20 = 70 ÷14 = 6 ╳ 15 = 12 ╳ 30 =

360 ÷6 = 37 ╳ 25 ╳ 4 =

2、计算下面各题，并用加法交换律验算。(4分)

168+239 476+508

3、计算下面各题，并用乘法交换律验算。(4分)

78 ╳ 46 65 ╳ 39

4、用简便方法计算下面各题。(12分)

54+87+13 27 ╳ 5 ╳ 4 950-178-422

39+144+61 15 ╳ 28 ╳ 2 32 ╳ 25

六、探索与应用。(8分)