(2011•大丰市)计算下面各题,能简算的要用简便方法计算.
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(2011•大丰市)计算下面各题,能简算的要用简便方法计算.
①250×8-245
②10.15-6.25-3.75+7.85
③
①250×8-245
②10.15-6.25-3.75+7.85
③
7 |
8 |
①250×8-245,
=2000-245,
=1755;
②10.15-6.25-3.75+7.85,
=10.15+7.85-(6.25+3.75),
=18-10,
=8;
③
7
8×
5
9+
5
9÷8,
=
7
8×
5
9+
5
9×
1
8,
=(
1
8+
7
8)×
5
9,
=1×
5
9,
=
5
9;
④24+5÷(3-2.5),
=24+5÷0.5,
=24+10,
=34;
⑤
10
13×(
3
4+1÷
5
6),
=
10
13×(
3
4+
6
5),
=
10
13×(
15
20+
24
20),
=
10
13×
39
20,
=
3
2;
⑥2÷[4×(
1
2-
1
3)]
=2÷[4×(
3
6-
2
6)],
=2÷[4×
1
6],
=2÷
=2000-245,
=1755;
②10.15-6.25-3.75+7.85,
=10.15+7.85-(6.25+3.75),
=18-10,
=8;
③
7
8×
5
9+
5
9÷8,
=
7
8×
5
9+
5
9×
1
8,
=(
1
8+
7
8)×
5
9,
=1×
5
9,
=
5
9;
④24+5÷(3-2.5),
=24+5÷0.5,
=24+10,
=34;
⑤
10
13×(
3
4+1÷
5
6),
=
10
13×(
3
4+
6
5),
=
10
13×(
15
20+
24
20),
=
10
13×
39
20,
=
3
2;
⑥2÷[4×(
1
2-
1
3)]
=2÷[4×(
3
6-
2
6)],
=2÷[4×
1
6],
=2÷