题目内容

简算.
①
1
1×2
+
1
2×3
+
1
3×4
+
1
4×5
+…+
1
199×200

②
382+498×381
382×498-116

③57.5-14.25-15
3
4

④
1
7
×102.31+10
6
7
×102.31
.
①
1
1×2
+
1
2×3
+
1
3×4
+
1
4×5
+…+
1
199×200
,
=1-
1
2
+
1
2
-
1
3
+
1
3
-
1
4
+
1
4
-
1
5
+…
1
199
-
1
200
,
=1-
1
200
,
=
199
200
;

②
382+498×381
382×498-116
,
=
382+498×381
(381+1)×498-116
,
=
382+498×381
381×498+498-116
,
=
382+498×381
382+498×381
,
=1;

③57.5-14.25-15
3
4
,
=57.5-14.25-15.75,
=57.5-(14.25+15.75),
=57.5-30,
=27.5;

④
1
7
×102.31+10
6
7
×102.31,
=(
1
7
+10
6
7
)×102.31,
=(10+1)×102.31,
=10×102.31+102.31,
=1023.1+102.31,
=1125.41.
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