题目内容
用递等式计算
①3÷
-
÷3
②
÷[
×(
+
)]
③(
-
+
)×12
④5.7-(1.9-1.3)
①3÷
3 |
7 |
3 |
7 |
②
9 |
20 |
1 |
2 |
2 |
3 |
4 |
5 |
③(
1 |
3 |
1 |
6 |
1 |
4 |
④5.7-(1.9-1.3)
分析:①同时运算除法,再算减法;
②先算小括号里面的加法,再算中括号里面的乘法,最后算括号外的除法;
③运用乘法分配律简算;
④先算小括号里面的减法,再算括号外的减法.
②先算小括号里面的加法,再算中括号里面的乘法,最后算括号外的除法;
③运用乘法分配律简算;
④先算小括号里面的减法,再算括号外的减法.
解答:解:①3÷
-
÷3,
=7-
,
=6
;
②
÷[
×(
+
)],
=
÷[
×
],
=
÷
,
=
;
③(
-
+
)×12,
=12×
-
×12+
×12,
=4-2+3,
=5;
④5.7-(1.9-1.3),
=5.7-0.6,
=5.1.
3 |
7 |
3 |
7 |
=7-
1 |
7 |
=6
6 |
7 |
②
9 |
20 |
1 |
2 |
2 |
3 |
4 |
5 |
=
9 |
20 |
1 |
2 |
22 |
15 |
=
9 |
20 |
11 |
15 |
=
27 |
44 |
③(
1 |
3 |
1 |
6 |
1 |
4 |
=12×
1 |
3 |
1 |
6 |
1 |
4 |
=4-2+3,
=5;
④5.7-(1.9-1.3),
=5.7-0.6,
=5.1.
点评:本题考查了四则混合运算,注意运算顺序和运算法则,灵活运用所学的运算定律进行简便计算.
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