题目内容
(2005?华亭县模拟)能简算的要简算
(1)4.9÷
+3.7÷
-1.6÷
(2)40-15×(
+
)
(3)98%×99+(1-1%)×2
(4)
×[
-(
-0.25)]
(5)[
-(0.2+
)×4.5]÷0.125.
(1)4.9÷
7 |
10 |
7 |
10 |
7 |
10 |
(2)40-15×(
2 |
3 |
1 |
5 |
(3)98%×99+(1-1%)×2
(4)
8 |
9 |
3 |
4 |
7 |
16 |
(5)[
15 |
4 |
1 |
3 |
分析:(1)把除以化成乘以,再运用乘法的分配律进行简算,
(2)先运用乘法的分配律进行简算,再算减法,
(3)原式=98×99%+99%×2,再运用乘法的分配律进行简算,
(4)先去小括号,先算中括号里的加法,再算中括号里的减法,最后算括号外的乘法,
(5)先运用乘法的分配律简算中括号里的乘法,再算中括号里的减法,最后算括号外的除法.
(2)先运用乘法的分配律进行简算,再算减法,
(3)原式=98×99%+99%×2,再运用乘法的分配律进行简算,
(4)先去小括号,先算中括号里的加法,再算中括号里的减法,最后算括号外的乘法,
(5)先运用乘法的分配律简算中括号里的乘法,再算中括号里的减法,最后算括号外的除法.
解答:解:(1)4.9÷
+3.7÷
-1.6÷
,
=4.9×
+3.7×
-1.6×
,
=(4.9+3.7-1.6)×
,
=(8.6-1.6)×
,
=7×
,
=10;
(2)40-15×(
+
),
=40-15×
-15×
,
=40-10-3,
=30-3,
=27;
(3)98%×99+(1-1%)×2,
=98×99%+99%×2,
=(98+2)×99%,
=100×99%,
=99;
(4)
×[
-(
-0.25)],
=
×[
-
+
],
=
×[1-
],
=
×
,
=
;
(5)[
-(0.2+
)×4.5]÷0.125,
=[
-0.2×4.5-
×4.5]÷0.125,
=[
-0.9-1.5]÷0.125,
=1.35÷0.125,
=1.08.
7 |
10 |
7 |
10 |
7 |
10 |
=4.9×
10 |
7 |
10 |
7 |
10 |
7 |
=(4.9+3.7-1.6)×
10 |
7 |
=(8.6-1.6)×
10 |
7 |
=7×
10 |
7 |
=10;
(2)40-15×(
2 |
3 |
1 |
5 |
=40-15×
2 |
3 |
1 |
5 |
=40-10-3,
=30-3,
=27;
(3)98%×99+(1-1%)×2,
=98×99%+99%×2,
=(98+2)×99%,
=100×99%,
=99;
(4)
8 |
9 |
3 |
4 |
7 |
16 |
=
8 |
9 |
3 |
4 |
7 |
16 |
1 |
4 |
=
8 |
9 |
7 |
16 |
=
8 |
9 |
9 |
16 |
=
1 |
2 |
(5)[
15 |
4 |
1 |
3 |
=[
15 |
4 |
1 |
3 |
=[
15 |
4 |
=1.35÷0.125,
=1.08.
点评:此题考查了四则混合运算顺序,要仔细观察算式的特点,灵活运用一些定律进行简便计算.
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