一年级下册《十几减6、5、4、3、2》预习学案

溧阳市外国语小学二年级组

&nbsp; &nbsp; 同学们,今天老师为同学们准备了《十几减6、5、4、3、2》的预习学案。这是苏教版小学数学一年级下册第9-10页的内容,主要结合具体情境,在学会口算十几减9、8、7的基础上,运用推算的方法学习十几减6、5、4、3、2。 <div><br></div> <font color="#ed2308">以下是微课指导学习:</font> <font color="#ed2308">例3</font>通过创设小兔采蘑菇的情境,寓教于乐。学生在学习中要充分掌握求<font color="#ed2308">总数</font>和求<font color="#ed2308">部分数</font>两个类型的解决问题。<div><br></div><h1><font color="#ed2308">计算方法:</font></h1><div>1.<font color="#167efb">想加算减</font></div> 例:11-6,想:6+( )=11&nbsp;&nbsp;<div>&nbsp; &nbsp;或<font color="#167efb">想减算减</font><br>&nbsp; &nbsp; &nbsp; &nbsp;11-5,由11-6=5&nbsp; &nbsp;想 11-5=?<div>2.<font color="#167efb">平十法</font>(先计算得出10)<br></div><div>&nbsp; &nbsp;例:11-6,先算11-1=10,再算10-5=5.</div><div>3.<font color="#167efb">破十法</font>(先用10去减)</div><div>&nbsp; &nbsp;例:11-6,先算10-6=4,再算1+4=5.</div></div><div>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;<font color="#ff8a00">破十法儿歌 <br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;</font><font color="#b06fbb">退位减,我会算<br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 十几减9,是几加1,<br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 十几减8,是几加2,<br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 十几减7,是几加3,<br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 十几减6,是几加4,<br>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 十几减5,是几加5.</font><br></div> &nbsp; &nbsp; <font color="#ed2308">【想想做做】</font>让学生通过题组练习逐渐优化算法。除了依据加减关系推算,也可以依据其他运算规律推算。通过不同形式的练习,帮助学生逐步形成计算能力,提高计算的速度和准确性。 <h3><font color="#ed2308">【当堂目标达成检测】</font></h3><div>11-6=&nbsp; &nbsp; &nbsp; &nbsp; 12-6=&nbsp; &nbsp; &nbsp; &nbsp; 13-6=&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;14-6=&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 15-6=</div><div>【巧算“<font color="#ed2308">十几减6</font>”的方法:把被减数个位上的数加“4”,就是十几减6的差。即减6个位加4。】</div><div><br></div><div>在⚪里填上“>”、“<”或“=”</div><div>13-6⚪8&nbsp; &nbsp; &nbsp; 14-5⚪7&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;6+7⚪14&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 11⚪19-9</div><div>13-5⚪8&nbsp; &nbsp; &nbsp; 11-6⚪6&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;4+8⚪13&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;7⚪11-4</div><div><br></div><div>在得数大于6的算式下面划“——”</div><div>14-8&nbsp; &nbsp; &nbsp; 13-4&nbsp; &nbsp; &nbsp; 12-3&nbsp; &nbsp; &nbsp; 11-7</div><div>16-8&nbsp; &nbsp; &nbsp; 17-9&nbsp; &nbsp; &nbsp; 15-9&nbsp; &nbsp; &nbsp; 14-5</div> <font color="#ed2308">&nbsp; &nbsp; 【课后拓展练习】</font> <div>解题过程:</div><div>&nbsp; &nbsp; &nbsp; 先找关键句。“数字看错了,得到结果9,妈妈告诉他,结果大了5”。从这句话可以知道正确的结果比9小5,列算式:9-5=4。把4带入原来的算式中,可以用前面介绍的方法计算出被减数。列算式:4+9=13。正确的算式应该是:13-9=4.</div><div><br></div><div>你做对了吗?</div> 制作:芮叶晨

十几

算式

减是

几加

推算

练习

减例

再算

破十法

被减数