题目内容
(2005?邳州市)下面各题怎样简便就怎样算.
(
+
)×
+
÷[1-(
+
)]
4×0.8×2.5×12.5
(2.8+3.85÷3.5)×4.6.
(
24 |
29 |
16 |
17 |
1 |
8 |
15 |
17 |
2 |
13 |
1 |
2 |
1 |
3 |
4×0.8×2.5×12.5
(2.8+3.85÷3.5)×4.6.
分析:(1)先运用乘法分配律简算,再运用加法结合律简算;
(2)先算小括号里面的加法,再算中括号里面的减法,最后算括号外的除法;
(3)运用乘法结合律简算;
(4)先算小括号里面的除法,再算小括号里面的加法,最后算括号外的乘法.
(2)先算小括号里面的加法,再算中括号里面的减法,最后算括号外的除法;
(3)运用乘法结合律简算;
(4)先算小括号里面的除法,再算小括号里面的加法,最后算括号外的乘法.
解答:解:(1)(
+
)×
+
,
=
×
+
×
+
,
=
+
+
,
=
+(
+
),
=
+1,
=1
;
(2)
÷[1-(
+
)],
=
÷[1-
],
=
÷
,
=
;
(3)4×0.8×2.5×12.5,
=(4×2.5)×(0.8×12.5),
=10×10,
=100;
(4)(2.8+3.85÷3.5)×4.6,
=(2.8+1.1)×4.6,
=3.9×4.6,
=17.94.
24 |
29 |
16 |
17 |
1 |
8 |
15 |
17 |
=
24 |
29 |
1 |
8 |
16 |
17 |
1 |
8 |
15 |
17 |
=
3 |
29 |
2 |
17 |
15 |
17 |
=
3 |
29 |
2 |
17 |
15 |
17 |
=
3 |
29 |
=1
3 |
29 |
(2)
2 |
13 |
1 |
2 |
1 |
3 |
=
2 |
13 |
5 |
6 |
=
2 |
13 |
1 |
6 |
=
12 |
13 |
(3)4×0.8×2.5×12.5,
=(4×2.5)×(0.8×12.5),
=10×10,
=100;
(4)(2.8+3.85÷3.5)×4.6,
=(2.8+1.1)×4.6,
=3.9×4.6,
=17.94.
点评:运算定律是常用的简便运算的方法,要熟练掌握,灵活运用.
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