脱式计算下面各题(能简算的要简算)①(1112-34)÷(2-12)②11×2+12×3+13×4+14×5+15×6+17×8③(57-421)÷521④30.8÷[14-(9.85+1.07)].

题目简介

脱式计算下面各题(能简算的要简算)①(1112-34)÷(2-12)②11×2+12×3+13×4+14×5+15×6+17×8③(57-421)÷521④30.8÷[14-(9.85+1.07)].

题目详情

脱式计算下面各题(能简算的要简算)
①(
11
12
-
3
4
)÷(2-
1
2

1
1×2
+
1
2×3
+
1
3×4
+
1
4×5
+
1
5×6
+
1
7×8

③(
5
7
-
4
21
)÷
5
21

④30.8÷[14-(9.85+1.07)].
题型:解答题难度:中档来源:不详

答案

①(class="stub"11
12
-
class="stub"3
4
)÷(2-class="stub"1
2
),
=(class="stub"11
12
-class="stub"9
12
)÷class="stub"3
2

=class="stub"1
6
×class="stub"2
3

=class="stub"1
9

class="stub"1
1×2
+class="stub"1
2×3
+class="stub"1
3×4
+class="stub"1
4×5
+class="stub"1
5×6
+class="stub"1
7×8

=(1-class="stub"1
2
)+(class="stub"1
2
-class="stub"1
3
)+(class="stub"1
3
-class="stub"1
4
)+(class="stub"1
4
-class="stub"1
5
)+(class="stub"1
5
-class="stub"1
6
)+(class="stub"1
7
-class="stub"1
8
),
=1-class="stub"1
2
+class="stub"1
2
-class="stub"1
3
+class="stub"1
3
-class="stub"1
4
+class="stub"1
4
-class="stub"1
5
+class="stub"1
5
-class="stub"1
6
+class="stub"1
7
-class="stub"1
8

=1-class="stub"1
6
+class="stub"1
7
-class="stub"1
8

=class="stub"5
6
+class="stub"1
56

=class="stub"143
168

③(class="stub"5
7
-
class="stub"4
21
)÷class="stub"5
21

=(class="stub"15
21
-class="stub"4
21
)×class="stub"21
5

=class="stub"11
21
×class="stub"21
5

=class="stub"11
5

=2class="stub"1
5

④30.8÷[14-(9.85+1.07)],
=30.8÷(14-10.92),
=30.8÷3.08,
=10.

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