题目内容
科学合理的计算
(1)2001×7
+1.375×2001+667÷
(2)7+
+
+
+…+
.
(1)2001×7
5 |
8 |
1 |
3 |
(2)7+
5 |
1×2 |
5 |
2×3 |
5 |
3×4 |
5 |
99×100 |
考点:分数的巧算
专题:计算问题(巧算速算)
分析:(1)根据除法的性质,把除法变为乘法后,运用乘法分配律简便计算;
(2)除7以外,把后面的加法算式利用乘法分配律以后,再根据
=
-
即可算出.
(2)除7以外,把后面的加法算式利用乘法分配律以后,再根据
1 |
n(n-1) |
1 |
n |
1 |
n-1 |
解答:
解:(1)2001×7
+1.375×2001+667÷
=2001×7
+1
×2001+667×3
=2001×7
+1
×2001+2001
=2001×(7
+1
+1)
=2001×10
=20010;
(2)7+
+
+
+…+
=7+5×(
+
+
+…+
)
=7+5×(1-
+
-
+
-
+…+
-
)
=7+5×(1-
)
=7+5×0.99
=7+4.95
=11.95
5 |
8 |
1 |
3 |
=2001×7
5 |
8 |
3 |
8 |
=2001×7
5 |
8 |
3 |
8 |
=2001×(7
5 |
8 |
3 |
8 |
=2001×10
=20010;
(2)7+
5 |
1×2 |
5 |
2×3 |
5 |
3×4 |
5 |
99×100 |
=7+5×(
1 |
1×2 |
1 |
2×3 |
1 |
3×4 |
1 |
99×100 |
=7+5×(1-
1 |
2 |
1 |
2 |
1 |
3 |
1 |
3 |
1 |
4 |
1 |
99 |
1 |
100 |
=7+5×(1-
1 |
100 |
=7+5×0.99
=7+4.95
=11.95
点评:本题考查简便计算,灵活运用运算定律是关键.
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