分析:(1)先求出50.8-(30+5.6□0.4)的值,再求出30+5.6□0.4的值,依此再确定运算符号;
(2)先求出7×9-160÷5,依此再确定运算符号;
(3)先求出(1.6+1.9)×1.4的值,依此再确定运算符号;
(4)先求出
□(
+
)的值,再求出
+
的值,依此再确定运算符号.
解答:解:(1)50.8-(30+5.6□0.4)
=34÷5
=6.8,
30+5.6□0.4
=50.8-6.8
=44,
因为30+5.6÷0.4
=30+14
=44,
所以[50.8-(30+5.6÷0.4)]×5=34;
(2)7×9-160÷5
=63-32
=31,
因为(21-5.5)×2
=15.5×2
=31,
所以7×9-160÷5=(21-5.5)×2,
(3)(1.6+1.9)×1.4
=3.5×1.4
=4.9,
因为29.4÷4.9=6,
所以29.4÷[(1.6+1.9)×1.4]=6;
(4)
□(
+
)
=
÷1
=
,
+
=
,
因为
×
=
,
所以
÷[
×
(+)]=1=1.
故答案为:÷;-,×;÷;×.
点评:考查了填符号组算式,根据运算顺序,由逆推法逐步解答即可.