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(2014•济南)简便运算(1)231×6.2+23.1×208-131×27;(2)734-1.125+(2.25-678);(3)1-2+3-4+5-6+7-8+9+97-98+99;(4)1+11+2+11+2+3+11+2+3+4+…+11+2+3+…+100.
题目详情
(2014•济南)简便运算
(1)231×6.2+23.1×208-131×27;
(2)7
-1.125+(2.25-6
);
(3)1-2+3-4+5-6+7-8+9+97-98+99;
(4)1+
+
+
+…+
.
(1)231×6.2+23.1×208-131×27;
(2)7
3 |
4 |
7 |
8 |
(3)1-2+3-4+5-6+7-8+9+97-98+99;
(4)1+
1 |
1+2 |
1 |
1+2+3 |
1 |
1+2+3+4 |
1 |
1+2+3+…+100 |
▼优质解答
答案和解析
(1)231×6.2+23.1×208-131×27
=231×6.2+231×20.8-131×27
=231×(6.2+20.8)-131×27
=231×27-131×27
=(231-131)×27
=100×27
=2700
(2)7
-1.125+(2.25-6
)
=7.75-1.125+(2.25-6.875)
=(7.75+2.25)-(1.125+6.875)
=10-8
=2
(3)1-2+3-4+5-6+7-8+9+97-98+99
=(1+99)+(-2-98)+…+50
=100-100+…+50
=50
(4)1+
+
+
+…+
=1+
+
+
+…+
=1+
+
+
+…+
=1+2×(
-
+
-
+
-
+…+
-
)
=1+2×(
-
)
=1+1-
=
=231×6.2+231×20.8-131×27
=231×(6.2+20.8)-131×27
=231×27-131×27
=(231-131)×27
=100×27
=2700
(2)7
3 |
4 |
7 |
8 |
=7.75-1.125+(2.25-6.875)
=(7.75+2.25)-(1.125+6.875)
=10-8
=2
(3)1-2+3-4+5-6+7-8+9+97-98+99
=(1+99)+(-2-98)+…+50
=100-100+…+50
=50
(4)1+
1 |
1+2 |
1 |
1+2+3 |
1 |
1+2+3+4 |
1 |
1+2+3+…+100 |
=1+
1 | ||
|
1 | ||
|
1 | ||
|
1 | ||
|
=1+
2 |
2×3 |
2 |
3×4 |
2 |
4×5 |
2 |
100×101 |
=1+2×(
1 |
2 |
1 |
3 |
1 |
3 |
1 |
4 |
1 |
4 |
1 |
5 |
1 |
100 |
1 |
101 |
=1+2×(
1 |
2 |
1 |
101 |
=1+1-
2 |
101 |
=
200 |
101 |
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