题目内容
(2009?兰州)
脱式计算.(能简算的要简算) (1)98.56-(8.56-3.28) |
(2)
|
(3)4.9×3.8+7.2×4.9-4.9 | |||||||||||||||
(4)
|
(5)(
|
分析:(1)先去括号,然后再计算;由于括号外的符号是减号,去括号时括号里面的运算符合要改变;
(2)把52分解成51+1,然后运用乘法分配律简算;
(3)运用乘法分配律简算;
(4)先算小括号里面的减法,再算括号外的除法,最后算加法;
(5)先同时运算小括号里面的减法和加法,再算括号外的除法.
(2)把52分解成51+1,然后运用乘法分配律简算;
(3)运用乘法分配律简算;
(4)先算小括号里面的减法,再算括号外的除法,最后算加法;
(5)先同时运算小括号里面的减法和加法,再算括号外的除法.
解答:解:(1)98.56-(8.56-3.28),
=98.56-8.56+3.28,
=90+3.28,
=93.28;
(2)
×52,
=
×(51+1),
=
×51+
×1,
=50+
,
=50
;
(3)4.9×3.8+7.2×4.9-4.9,
=4.9×(3.8+7.2-1),
=4.9×10,
=49;
(4)
+(
-
)÷
,
=
+
÷
,
=
+
,
=1;
(5)(
-
)÷(
+
),
=
÷
,
=
.
=98.56-8.56+3.28,
=90+3.28,
=93.28;
(2)
50 |
51 |
=
50 |
51 |
=
50 |
51 |
50 |
51 |
=50+
50 |
51 |
=50
50 |
51 |
(3)4.9×3.8+7.2×4.9-4.9,
=4.9×(3.8+7.2-1),
=4.9×10,
=49;
(4)
9 |
11 |
7 |
12 |
1 |
2 |
11 |
24 |
=
9 |
11 |
1 |
12 |
11 |
24 |
=
9 |
11 |
2 |
11 |
=1;
(5)(
2 |
3 |
7 |
12 |
2 |
7 |
1 |
8 |
=
1 |
12 |
23 |
56 |
=
14 |
69 |
点评:此题主要考查小数、分数的四则混合运算的运算顺序和应用运算定律进行简便计算.
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