选择合理的方法进行计算.(1)715+1921+221(2)10-712-512(3)58+45-38+15(4)0.25+1115+34+415(5)3-14-13-34(6)15-5÷12-712

题目简介

选择合理的方法进行计算.(1)715+1921+221(2)10-712-512(3)58+45-38+15(4)0.25+1115+34+415(5)3-14-13-34(6)15-5÷12-712

题目详情

选择合理的方法进行计算.
(1)
7
15
+
19
21
+
2
21
(2)10-
7
12
-
5
12
(3)
5
8
+
4
5
-
3
8
+
1
5
(4)0.25+
11
15
+
3
4
+
4
15
(5)3-
1
4
-
1
3
-
3
4
(6)15-5÷12-
7
12
题型:解答题难度:中档来源:不详

答案

(1)class="stub"7
15
+class="stub"19
21
+class="stub"2
21

=class="stub"7
15
+(class="stub"19
21
+class="stub"2
21
),
=class="stub"7
15
+1,
=1class="stub"7
15



(2)10-class="stub"7
12
-class="stub"5
12

=10-(class="stub"7
12
+class="stub"5
12
),
=10-1,
=9;


(3)class="stub"5
8
+class="stub"4
5
-class="stub"3
8
+class="stub"1
5

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


(4)0.25+class="stub"11
15
+class="stub"3
4
+class="stub"4
15

=(0.25+0.75)+(class="stub"11
15
+class="stub"4
15
),
=1+1,
=2;

(5)3-class="stub"1
4
-class="stub"1
3
-class="stub"3
4

=(3-class="stub"1
3
)-(class="stub"1
4
+class="stub"3
4
),
=2class="stub"2
3
-1,
=1class="stub"2
3


(6)15-5÷12-class="stub"7
12

=15-(class="stub"5
12
+class="stub"7
12
),
=15-1,
=14.

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