数学学习乐园讨论与解答（11―20） 标签：速算与巧算
<p><strong><font face=" ,Arial">11</font></strong><font face=" ,Arial"> </font></p><p><b><font face=" ,Arial"> </font></b></p><p><b><font face=" ,Arial">12</font></b></p><p><b><font face=" ,Arial"> </font></b></p><p><b><font face=" ,Arial">13</font></b><b><font face=" ,Arial">17</font></b><font face=" ,Arial"> </font></p><p><font face=" ,Arial">5</font><font face=" ,Arial">13</font><font face=" ,Arial">14</font><font face=" ,Arial">15</font><font face=" ,Arial">15</font><font face=" ,Arial">16</font><font face=" ,Arial">17</font><font face=" ,Arial">(Johannes Kepler</font><font face=" ,Arial">2023</font><font face=" ,Arial">2023)</font></p><p><font face=" ,Arial">13</font><font face=" ,Arial">a</font><font face=" ,Arial">b</font><font face=" ,Arial">ab</font><font face=" ,Arial">a=2b</font><font face=" ,Arial">2</font><font face="宋体" lang="ZH-CN">π</font><font face=" ,Arial">b</font><font face=" ,Arial" size="2">2</font><font face=" ,Arial">b</font><font face=" ,Arial">3</font><font face=" ,Arial">3</font></p><p><font face=" ,Arial">(a+b)</font><font face=" ,Arial">(Srinivasa Ramanujan)</font><font face=" ,Arial">2023</font></p><p><b><font face=" ,Arial"> </font></b></p><p><b><font face=" ,Arial">18</font></b></p><p><font face=" ,Arial">9</font><font face=" ,Arial">(3</font><font face=" ,Arial">3</font><font face=" ,Arial">)</font><font face=" ,Arial">2</font><font face=" ,Arial">1</font><font face=" ,Arial">1</font><font face=" ,Arial">8</font><b><font face=" ,Arial"> </font></b></p><p><b><font face=" ,Arial">19</font></b></p><p><font face=" ,Arial">A</font><font face=" ,Arial">D</font></p><p><font face="宋体" lang="ZH-CN"> </font></p><p><b><font face=" ,Arial">20</font></b></p><p><b><font face=" ,Arial"></font></b></p>
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