题目内容
用简便方法计算,写出必要的简算过程.
×
+
×
×16.3+
×2.8
4×5
+5×6
+6×7
.
5 |
6 |
5 |
9 |
5 |
9 |
1 |
6 |
8 |
17 |
2 |
17 |
4×5
3 |
4 |
4 |
5 |
5 |
6 |
分析:(1)运用乘法分配律简算;
(2)先根据积不变规律把
×2.8变成
×0.7再运用乘法分配律简算;
(3)先把每个带分数化成一个整数与一个分数相加的形式,再运用乘法分配律简算.
(2)先根据积不变规律把
2 |
17 |
8 |
17 |
(3)先把每个带分数化成一个整数与一个分数相加的形式,再运用乘法分配律简算.
解答:解:(1)
×
+
×
=(
+
)×
=1×
=
;
(2)
×16.3+
×2.8
=
×16.3+
×0.7
=
×(16.3+0.7)
=
×17
=8;
(3)4×5
+5×6
+6×7
=4×(5+
)+5×(6+
)+6×(7+
)
=(4×5+4×
)+(5×6+5×
)+(6×7+6×
)
=(20+3)+(30+4)+(42+5)
=23+34+47
=23+47+34
=70+34
=104.
5 |
6 |
5 |
9 |
5 |
9 |
1 |
6 |
=(
5 |
6 |
1 |
6 |
5 |
9 |
=1×
5 |
9 |
=
5 |
9 |
(2)
8 |
17 |
2 |
17 |
=
8 |
17 |
8 |
17 |
=
8 |
17 |
=
8 |
17 |
=8;
(3)4×5
3 |
4 |
4 |
5 |
5 |
6 |
=4×(5+
3 |
4 |
4 |
5 |
5 |
6 |
=(4×5+4×
3 |
4 |
4 |
5 |
5 |
6 |
=(20+3)+(30+4)+(42+5)
=23+34+47
=23+47+34
=70+34
=104.
点评:此题是考查四则混合运算,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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