题目内容
| 合理、灵活地计算. 2n×
|
| 2着×(
| ||||||||||||||||||
|
| (
|
(1)24×
-
=
-
,
=
;
(2)
×
+
×
=(
+
)×
,
=1×
,
=
;
(3)28×(
+
-
)
=28×
+28×
-28×
,
=8+18-7,
=19;
(4)
×
×
=
×
,
=
;
(5)
×299+
=(299+1)×
,
=3得得×
,
=7得;
(中)(
-
)×
×2
=
×
×2,
=
.
| 5 |
| 3中 |
| 3 |
| 8 |
=
| 1得 |
| 3 |
| 3 |
| 8 |
=
| 71 |
| 24 |
(2)
| 7 |
| 18 |
| 1 |
| 4 |
| 3 |
| 4 |
| 7 |
| 18 |
=(
| 1 |
| 4 |
| 3 |
| 4 |
| 7 |
| 18 |
=1×
| 7 |
| 18 |
=
| 7 |
| 18 |
(3)28×(
| 2 |
| 7 |
| 9 |
| 14 |
| 1 |
| 4 |
=28×
| 2 |
| 7 |
| 9 |
| 14 |
| 1 |
| 4 |
=8+18-7,
=19;
(4)
| 4 |
| 9 |
| 3 |
| 4 |
| 9 |
| 11 |
=
| 1 |
| 3 |
| 9 |
| 11 |
=
| 3 |
| 11 |
(5)
| 7 |
| 3得 |
| 7 |
| 3得 |
=(299+1)×
| 7 |
| 3得 |
=3得得×
| 7 |
| 3得 |
=7得;
(中)(
| 4 |
| 5 |
| 1 |
| 2 |
| 2 |
| 3 |
=
| 3 |
| 1得 |
| 2 |
| 3 |
=
| 2 |
| 5 |
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