2014冀教版数学一下《二、20以内的减法》ppt课件1[www.edudown.net].ppt

1、20以内的退位减法,二20以内的减法(第九课时),119,118,117,116,114,112,129,128,126,125,123,138,137,135,134,149,147,146,145,159,158,157,156,169,168,178,189,127,139,179,148,167,136,115,124,113,119,118,117,116,115,114,113,112,129,128,127,126,125,124,123,139,138,137,136,135,134,149,148,147,146,145,159,158,157,156,169,168,167

2、,179,178,189,竖着看，第一列的算式有什么规律？得数有什么规律？,112,竖着看，第一列的算式有什么规律？得数有什么规律？,119,118,117,116,115,114,113,112,129,128,127,126,125,124,123,139,138,137,136,135,134,149,148,147,146,145,159,158,157,156,169,168,167,179,178,189,竖着看，第一列的算式有什么规律？得数有什么规律？,越来越大,不变,越来越大,不变,119,118,117,116,115,114,113,112,129,128,127,126,

3、125,124,123,139,138,137,136,135,134,149,148,147,146,145,159,158,157,156,169,168,167,179,178,189,竖着看，每一列的算式有什么规律？得数有什么规律？,越来越大,不变,越来越大,不变,2,3,4,5,6,7,8,9,3,4,5,6,7,8,9,4,5,6,7,8,9,5,6,7,8,9,6,7,8,9,7,8,9,8,9,9,119,118,117,116,115,114,113,112,129,128,127,126,125,124,123,139,138,137,136,135,134,149,148

4、,147,146,145,159,158,157,156,169,168,167,179,178,189,5,6,7,8,9,3,4,2,5,6,7,8,9,3,4,5,6,7,8,9,4,5,6,7,8,9,6,7,8,9,7,8,9,8,9,9,横着看，每一行的算式有什么规律？得数有什么规律？,仔细观察减法表，你还能发现什么规律？,119,118,117,116,115,114,113,112,129,128,127,126,125,124,123,139,138,137,136,135,134,149,148,147,146,145,159,158,157,156,169,168,167

5、,179,178,189,2,3,4,5,6,7,8,9,119,118,129,139,149,159,169,179,189,128,138,148,158,168,178,117,116,115,114,113,112,127,126,125,124,123,137,136,135,134,147,146,145,157,156,167,赶快动手整理一下减法表吧！把你的整理结果写在书上第24页。,观察减法表，那些算式的结果是6 ？,我的朋友在哪里？,115,126,137,148,159,6,7,4,125,136,147,158,169,117,128,139,写算式,9 8 17,自己选择三个数，再写出一组算式。,8 9 17,17 8 9,17 9 8,用9、8、17写出两个加法算 式和两个减法算式。,提问题,我拔了13个萝卜。,我拔了7个萝卜。,我拔了6个萝卜。,明明,丫丫,童童,三只兔子一共拔了几个萝卜呢？,137626,你还能提出哪些问题呢？,这个难不倒我！,15 6 9,速度大比拼