七年级-有理数的加法-10-众享题库-众享学科测评

1编号：2014题型：计算题测试正确率：73.47%

$1+\frac{1}{1+2}+\frac{1}{1+2+3}+...+\frac{1}{1+2+3+...+100}$

查看相关视频查看答案及解析

2编号：2011题型：单选题测试正确率：41.5%

$\frac{1}{3\times 5}+\frac{1}{5\times 7}+...+\frac{1}{2009\times 2011}$
= $\frac{1}{2}(\frac{1}{3}-\frac{1}{5})+\frac{1}{2}(\frac{1}{5}-\frac{1}{7})+...+\frac{1}{2}(\frac{1}{2009}-\frac{1}{2011})$    ①
= $\frac{1}{2}(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{2009}-\frac{1}{2011})$     ②
= $\frac{1}{2}(\frac{1}{3}-\frac{1}{2011})$   ③
= $\frac{1044}{6033}$   ④   下列步骤错误的是（    ）

查看相关视频查看答案及解析

3编号：2003题型：计算题测试正确率：77.19%

计算： $\frac{1}{2}+(\frac{1}{3}+\frac{2}{3})+(\frac{1}{4}+\frac{2}{4}+\frac{3}{4})+...+(\frac{1}{60}+\frac{2}{60}+...+\frac{59}{60})$

查看相关视频查看答案及解析

4编号：1995题型：单选题测试正确率：27.44%

下列哪一步计算错误 $[-\frac{7}{5}\times(-2\frac{1}{2})-1]\div9\div\frac{1}{(-0.75)^{2}}-|2+(-\frac{1}{2})^{3}\times5^{2}|$
解：原式= $(\frac{7}{2}-1)\times\frac{1}{9}\times\frac{16}{9}-|2+(-\frac{1}{2})^{3}\times5^{2}|$ ①
= $[-\frac{7}{5}\times(-\frac{5}{2})-1]\times\frac{1}{9}\times(\frac{4}{3})^{2}-|2+\frac{25}{8}|$ ②
= $\frac{5}{2}\times\frac{1}{9}\times\frac{16}{9}-\frac{41}{8}$ ③
= $\frac{40}{81}-\frac{41}{8}$ ④