题目内容

脱式计算(能简算的要简算)
(1)
9
20
÷[
1
2
×(
2
5
+
4
5
)]

(2)
20
13
×
17
9
-
8
9
÷
13
20

(3)1999+999×999
(4)33333×66666.
(1)
9
20
÷[
1
2
×(
2
5
+
4
5
)]

=
9
20
÷[
1
2
×
6
5
]

=
9
20
×
5
3

=
3
4


(2)
20
13
×
17
9
-
8
9
÷
13
20

=
20
13
×
17
9
-
8
9
×
20
13

=
20
13
×(
17
9
-
8
9
),
=
20
13
×1,
=
20
13


(3)1999+999×999,
=1999+(1000-1)×999,
=1999+1000×999-999,
=1999+999000-999,
=1999-999+999000,
=1000000;

(4)33333×66666,
=22222×1.5×66666,
=22222×(1.5×666666)
=22222×99999,
=22222×(100000-1),
=2222200000-22222,
=2222177778.
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