题目内容
(2010?万安县)脱式计算能用简算要简算:
(1)19.875-(5.5+8
)
(2)[
+(6.4-4
)×
]÷
(3)(
+
)×23×19
(4)27.2×
+3
×12.5%+0.125.
(1)19.875-(5.5+8
7 |
8 |
(2)[
1 |
3 |
2 |
5 |
5 |
2 |
14 |
9 |
(3)(
1 |
19 |
1 |
23 |
(4)27.2×
1 |
8 |
4 |
5 |
分析:(1)去括号后交换两个减数的位置,可以使计算变得简单;
(2)按四则混合运算的计算法则进行计算;
(3)运用乘法分配律分配简算;
(4)分数、百分数化成小数后运用乘法分配律进行简算.
(2)按四则混合运算的计算法则进行计算;
(3)运用乘法分配律分配简算;
(4)分数、百分数化成小数后运用乘法分配律进行简算.
解答:解:(1)19.875-(5.5+8
),
=19.875-5.5-8
,
=19.875-8
-5.5,
=19.875-8.875-5.5,
=11-5.5,
=5.5;
(2)[
+(6.4-4
)×
]÷
,
=[
+(6.4-4.4)×
]÷
,
=[
+2×
]÷
,
=[
+5]×
,
=
×
,
=
;
(3)(
+
)×23×19,
=
×23×19+
×23×19,
=23+19,
=42;
(4)27.2×
+3
×12.5%+0.125,
=27.2×0.125+3.8×0.125+0.125,
=(27.2+3.8+1)×0.125,
=32×0.125,
=4.
7 |
8 |
=19.875-5.5-8
7 |
8 |
=19.875-8
7 |
8 |
=19.875-8.875-5.5,
=11-5.5,
=5.5;
(2)[
1 |
3 |
2 |
5 |
5 |
2 |
14 |
9 |
=[
1 |
3 |
5 |
2 |
14 |
9 |
=[
1 |
3 |
5 |
2 |
14 |
9 |
=[
1 |
3 |
9 |
14 |
=
16 |
3 |
9 |
14 |
=
24 |
7 |
(3)(
1 |
19 |
1 |
23 |
=
1 |
19 |
1 |
23 |
=23+19,
=42;
(4)27.2×
1 |
8 |
4 |
5 |
=27.2×0.125+3.8×0.125+0.125,
=(27.2+3.8+1)×0.125,
=32×0.125,
=4.
点评:此题考查整数、分数、小数、百分数四则混合运算,计算同时注意运用定律进行简算.
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