题目内容
(2008?宝应县)
计算下列各题,能简算的要简算: (1)(4800÷75+36)×12 |
(2)
|
(3)3.8×99+3.8 | ||||||||||
(4)42×
|
(5)(
|
(6)7.8-3.6+2.2-6.4. |
分析:(1)按运算顺序计算,先算括号内的除法,再算括号内的加法,最后算括号外的;
(2)按运算顺序计算,先算小括号内的,再算中括号内的,最后算括号外的;
(3)把3.8看作3.8×1,利用乘法分配律的逆运算简算;
(4)把42看作41+1,然后用乘法分配律简算;
(5)把除法改为乘法后,用乘法分配律计算;
(6)运用加法交换律和结合律以及减法的性质简算.
(2)按运算顺序计算,先算小括号内的,再算中括号内的,最后算括号外的;
(3)把3.8看作3.8×1,利用乘法分配律的逆运算简算;
(4)把42看作41+1,然后用乘法分配律简算;
(5)把除法改为乘法后,用乘法分配律计算;
(6)运用加法交换律和结合律以及减法的性质简算.
解答:解:(1)(4800÷75+36)×12,
=(64+36)×12
=100×12,
=1200;
(2)
÷[
×(
-
)],
=
÷[
×(
-
)],
=
÷[
×
],
=
÷
,
=
×9,
=2;
(3)3.8×99+3.8,
=3.8×(99+1)
=3.8×100,
=380;
(4)42×
,
=(41+1)×
,
=41×
+
,
=40
;
(5)(
+
-
)÷
,
=
×24+
×24-
×24,
=12+16-6,
=22;
(6)7.8-3.6+2.2-6.4,
=7.8+2.2-(3.6+6.4),
=10-10,
=0.
=(64+36)×12
=100×12,
=1200;
(2)
2 |
9 |
5 |
6 |
4 |
5 |
2 |
3 |
=
2 |
9 |
5 |
6 |
12 |
15 |
10 |
15 |
=
2 |
9 |
5 |
6 |
2 |
15 |
=
2 |
9 |
1 |
9 |
=
2 |
9 |
=2;
(3)3.8×99+3.8,
=3.8×(99+1)
=3.8×100,
=380;
(4)42×
40 |
41 |
=(41+1)×
40 |
41 |
=41×
40 |
41 |
40 |
41 |
=40
40 |
41 |
(5)(
1 |
2 |
2 |
3 |
1 |
4 |
1 |
24 |
=
1 |
2 |
2 |
3 |
1 |
4 |
=12+16-6,
=22;
(6)7.8-3.6+2.2-6.4,
=7.8+2.2-(3.6+6.4),
=10-10,
=0.
点评:此题重点考查学生对运算顺序的掌握情况,以及运用运算定律、运算性质以及其它运算技巧,进行简算的能力.
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