和差積的奇偶性ppt課件

1、因數(shù)與倍數(shù)因數(shù)與倍數(shù)和、差、積的奇偶性和、差、積的奇偶性把下面各數(shù)分別填在合適的圈內(nèi)。把下面各數(shù)分別填在合適的圈內(nèi)。39 48 51 207 420 801 8976奇數(shù)奇數(shù)偶數(shù)偶數(shù)513920780148420 8976說(shuō)說(shuō)你是怎么判斷的？說(shuō)說(shuō)你是怎么判斷的？在整數(shù)中，是在整數(shù)中，是2的倍數(shù)的的倍數(shù)的數(shù)就是偶數(shù)，否則就是數(shù)就是偶數(shù)，否則就是奇數(shù)。奇數(shù)。個(gè)位上是個(gè)位上是0、2、4、6、8的數(shù)是偶數(shù)；個(gè)位上是的數(shù)是偶數(shù)；個(gè)位上是1、3、5、7、9的數(shù)是的數(shù)是奇數(shù)。奇數(shù)。奇數(shù)與偶數(shù)的和是奇數(shù)還是偶數(shù)？奇數(shù)與奇數(shù)的和奇數(shù)與偶數(shù)的和是奇數(shù)還是偶數(shù)？奇數(shù)與奇數(shù)的和是奇數(shù)還是偶數(shù)？偶數(shù)與偶數(shù)的和呢？是奇數(shù)

2、還是偶數(shù)？偶數(shù)與偶數(shù)的和呢？奇數(shù)奇數(shù)偶數(shù)偶數(shù)奇數(shù)奇數(shù)? ?偶數(shù)？偶數(shù)？奇數(shù)奇數(shù)奇數(shù)奇數(shù)奇數(shù)？奇數(shù)？偶數(shù)？偶數(shù)？偶數(shù)偶數(shù)偶數(shù)偶數(shù)奇數(shù)？奇數(shù)？偶數(shù)？偶數(shù)？從題目中你知道了什么？從題目中你知道了什么？閱讀與理解閱讀與理解題目讓我們對(duì)奇題目讓我們對(duì)奇數(shù)、偶數(shù)的和做數(shù)、偶數(shù)的和做一些探索。一些探索。我把問(wèn)題表示我把問(wèn)題表示成這樣成這樣我隨便找?guī)讉€(gè)奇數(shù)、偶我隨便找?guī)讉€(gè)奇數(shù)、偶數(shù)，加起來(lái)看一看。數(shù)，加起來(lái)看一看。奇數(shù)：奇數(shù)：5， 7， 9， 11，偶數(shù)：偶數(shù)：8，12，20，24，571279165813781581220122436奇數(shù)奇數(shù)奇數(shù)奇數(shù)偶數(shù)偶數(shù)奇數(shù)奇數(shù)偶數(shù)偶數(shù)奇數(shù)奇數(shù)偶數(shù)偶數(shù)偶數(shù)偶數(shù)偶數(shù)偶數(shù)奇

3、數(shù)與偶數(shù)的和是奇數(shù)還是偶數(shù)？奇數(shù)與奇數(shù)的和奇數(shù)與偶數(shù)的和是奇數(shù)還是偶數(shù)？奇數(shù)與奇數(shù)的和是奇數(shù)還是偶數(shù)？偶數(shù)與偶數(shù)的和呢？是奇數(shù)還是偶數(shù)？偶數(shù)與偶數(shù)的和呢？你怎么想？你怎么想？分析與解答分析與解答奇數(shù)除以奇數(shù)除以2余余1奇數(shù)：奇數(shù)：偶數(shù)：偶數(shù)：偶數(shù)除以偶數(shù)除以2沒(méi)有余數(shù)沒(méi)有余數(shù)奇數(shù)加偶數(shù)的和除以奇數(shù)加偶數(shù)的和除以2還余還余1，所以，奇數(shù)，所以，奇數(shù)偶數(shù)偶數(shù)奇數(shù)。奇數(shù)。奇數(shù)加奇數(shù)的和除以奇數(shù)加奇數(shù)的和除以2沒(méi)有余數(shù)，所以，奇數(shù)沒(méi)有余數(shù)，所以，奇數(shù)奇數(shù)奇數(shù)偶數(shù)。偶數(shù)。偶數(shù)加偶數(shù)的和除以偶數(shù)加偶數(shù)的和除以2沒(méi)有余數(shù)，所以，偶數(shù)沒(méi)有余數(shù)，所以，偶數(shù)偶數(shù)偶數(shù)偶數(shù)。偶數(shù)。奇數(shù)與偶數(shù)的和是奇數(shù)還是偶數(shù)？奇數(shù)與

4、奇數(shù)的和奇數(shù)與偶數(shù)的和是奇數(shù)還是偶數(shù)？奇數(shù)與奇數(shù)的和是奇數(shù)還是偶數(shù)？偶數(shù)與偶數(shù)的和呢？是奇數(shù)還是偶數(shù)？偶數(shù)與偶數(shù)的和呢？你怎么想？你怎么想？分析與解答分析與解答奇數(shù)與偶數(shù)的和是奇數(shù)還是偶數(shù)？奇數(shù)與奇數(shù)的和奇數(shù)與偶數(shù)的和是奇數(shù)還是偶數(shù)？奇數(shù)與奇數(shù)的和是奇數(shù)還是偶數(shù)？偶數(shù)與偶數(shù)的和呢？是奇數(shù)還是偶數(shù)？偶數(shù)與偶數(shù)的和呢？奇數(shù)奇數(shù)奇數(shù)奇數(shù)奇數(shù)奇數(shù)偶數(shù)偶數(shù)偶數(shù)偶數(shù)偶數(shù)偶數(shù)偶數(shù)偶數(shù)奇數(shù)奇數(shù)偶數(shù)偶數(shù)所以，你們的所以，你們的結(jié)論是結(jié)論是奇數(shù)與偶數(shù)的和是奇數(shù)還是偶數(shù)？奇數(shù)與奇數(shù)的和奇數(shù)與偶數(shù)的和是奇數(shù)還是偶數(shù)？奇數(shù)與奇數(shù)的和是奇數(shù)還是偶數(shù)？偶數(shù)與偶數(shù)的和呢？是奇數(shù)還是偶數(shù)？偶數(shù)與偶數(shù)的和呢？奇數(shù)奇數(shù)奇數(shù)奇數(shù)奇數(shù)

5、奇數(shù)偶數(shù)偶數(shù)偶數(shù)偶數(shù)偶數(shù)偶數(shù)偶數(shù)偶數(shù)奇數(shù)奇數(shù)偶數(shù)偶數(shù)所以，你們的所以，你們的結(jié)論是結(jié)論是奇數(shù)偶數(shù)（奇數(shù)偶數(shù)（ ）偶數(shù)奇數(shù)（偶數(shù)奇數(shù)（ ）奇數(shù)奇數(shù)（奇數(shù)奇數(shù)（ ）偶數(shù)偶數(shù)（偶數(shù)偶數(shù)（ ）奇數(shù)奇數(shù)偶數(shù)偶數(shù)偶數(shù)偶數(shù)奇數(shù)奇數(shù)奇數(shù)與偶數(shù)的和是奇數(shù)還是偶數(shù)？奇數(shù)與奇數(shù)的和奇數(shù)與偶數(shù)的和是奇數(shù)還是偶數(shù)？奇數(shù)與奇數(shù)的和是奇數(shù)還是偶數(shù)？偶數(shù)與偶數(shù)的和呢？是奇數(shù)還是偶數(shù)？偶數(shù)與偶數(shù)的和呢？534319853所以，奇數(shù)所以，奇數(shù)偶數(shù)偶數(shù)奇數(shù)奇數(shù)回顧與反思回顧與反思這個(gè)結(jié)論正確嗎？這個(gè)結(jié)論正確嗎？我可以再找一些我可以再找一些大數(shù)試一試。大數(shù)試一試。同學(xué)們還有其他方法嗎？同學(xué)們還有其他方法嗎？你覺(jué)得哪種方法好？你覺(jué)得哪

6、種方法好？1.30個(gè)學(xué)生要分成甲、乙兩隊(duì)。如果甲隊(duì)人數(shù)為奇數(shù)，乙個(gè)學(xué)生要分成甲、乙兩隊(duì)。如果甲隊(duì)人數(shù)為奇數(shù)，乙隊(duì)人數(shù)為奇數(shù)還是偶數(shù)？如果甲隊(duì)人數(shù)為偶數(shù)呢？隊(duì)人數(shù)為奇數(shù)還是偶數(shù)？如果甲隊(duì)人數(shù)為偶數(shù)呢？30是偶數(shù)，甲隊(duì)人數(shù)為奇是偶數(shù)，甲隊(duì)人數(shù)為奇數(shù)，奇數(shù)奇數(shù)偶數(shù)，數(shù)，奇數(shù)奇數(shù)偶數(shù)，所以，乙隊(duì)人數(shù)是奇數(shù)。所以，乙隊(duì)人數(shù)是奇數(shù)。30是偶數(shù)，甲隊(duì)人數(shù)是偶數(shù)，甲隊(duì)人數(shù)是偶數(shù)，偶數(shù)偶數(shù)是偶數(shù)，偶數(shù)偶數(shù)偶數(shù)，所以，乙隊(duì)偶數(shù)，所以，乙隊(duì)人數(shù)是偶數(shù)。人數(shù)是偶數(shù)。2. 奇數(shù)與奇數(shù)的積是奇數(shù)還是偶數(shù)？奇數(shù)與偶數(shù)的奇數(shù)與奇數(shù)的積是奇數(shù)還是偶數(shù)？奇數(shù)與偶數(shù)的 積是奇數(shù)還是偶數(shù)？偶數(shù)與偶數(shù)的積呢？積是奇數(shù)還是偶數(shù)？偶數(shù)與偶

7、數(shù)的積呢？5735796358407856812961424336奇數(shù)奇數(shù)奇數(shù)奇數(shù)奇數(shù)奇數(shù)奇數(shù)奇數(shù)偶數(shù)偶數(shù)偶數(shù)偶數(shù)偶數(shù)偶數(shù)偶數(shù)偶數(shù)偶數(shù)偶數(shù)選擇，把正確答案的序號(hào)填在括號(hào)里。選擇，把正確答案的序號(hào)填在括號(hào)里。（1 1）3 32 24545的和是（的和是（ ）A A一定是奇數(shù)一定是奇數(shù) B B 一定是偶數(shù)一定是偶數(shù) C C可能是奇數(shù)可能是偶數(shù)可能是奇數(shù)可能是偶數(shù)A A（2 2）63637979的差是（的差是（ ）A A一定是奇數(shù)一定是奇數(shù) B B 一定是偶數(shù)一定是偶數(shù) C C可能是奇數(shù)可能是偶數(shù)可能是奇數(shù)可能是偶數(shù)C C（3 3）5 5 3232的差是（的差是（ ）A A一定是奇數(shù)一定是奇數(shù) B

8、B 一定是偶數(shù)一定是偶數(shù) C C可能是奇數(shù)可能是偶數(shù)可能是奇數(shù)可能是偶數(shù)B B（4 4）大于）大于2 2的兩個(gè)質(zhì)數(shù)的積是（的兩個(gè)質(zhì)數(shù)的積是（ ）A A 質(zhì)數(shù)質(zhì)數(shù) B B 合數(shù)合數(shù) C C 奇數(shù)奇數(shù) D D 偶數(shù)偶數(shù)C C（5 5）兩個(gè)質(zhì)數(shù)的和是（）兩個(gè)質(zhì)數(shù)的和是（ ）A A 質(zhì)數(shù)質(zhì)數(shù) B B 合數(shù)合數(shù) C C 奇數(shù)或偶數(shù)奇數(shù)或偶數(shù) D D 偶數(shù)偶數(shù)C C（6 6）1313是一個(gè)質(zhì)數(shù)，它的倍數(shù)是（是一個(gè)質(zhì)數(shù)，它的倍數(shù)是（ ）A A 質(zhì)數(shù)質(zhì)數(shù) B B 合數(shù)合數(shù) C C 質(zhì)數(shù)或合數(shù)質(zhì)數(shù)或合數(shù) D D 以上都不對(duì)以上都不對(duì)C C從從1 1、2 2、3 3、4 4、5 5、6 6中任意取出兩個(gè)數(shù)相加。中

9、任意取出兩個(gè)數(shù)相加。和為偶數(shù)的可能性大還是和為奇數(shù)的可能性大？和為偶數(shù)的可能性大還是和為奇數(shù)的可能性大？和為質(zhì)數(shù)的可能性大還是和為合數(shù)的可能性大？和為質(zhì)數(shù)的可能性大還是和為合數(shù)的可能性大？1+231+341+451+561+672+352+462+572+683+473+583+694+594+6105+611奇數(shù)共奇數(shù)共9個(gè)個(gè)偶數(shù)共偶數(shù)共6個(gè)個(gè)質(zhì)數(shù)共質(zhì)數(shù)共7個(gè)個(gè)合數(shù)共合數(shù)共8個(gè)個(gè)96和為奇數(shù)的可能性大。和為奇數(shù)的可能性大。78和為合數(shù)的可能性大。和為合數(shù)的可能性大。 三個(gè)不同質(zhì)數(shù)的和是三個(gè)不同質(zhì)數(shù)的和是8282，這三個(gè)質(zhì)數(shù)的積最大是可能，這三個(gè)質(zhì)數(shù)的積最大是可能是（是（ ） 想；因?yàn)槌讼耄?/p>

10、因?yàn)槌?以外所有的質(zhì)數(shù)都是奇數(shù)，三個(gè)質(zhì)數(shù)相以外所有的質(zhì)數(shù)都是奇數(shù)，三個(gè)質(zhì)數(shù)相加的和是偶數(shù)，必定有一個(gè)是質(zhì)數(shù)加的和是偶數(shù)，必定有一個(gè)是質(zhì)數(shù)2。82280，剩下，剩下的兩個(gè)質(zhì)數(shù)的和是的兩個(gè)質(zhì)數(shù)的和是80，兩個(gè)數(shù)和一定，差越小，積越大。，兩個(gè)數(shù)和一定，差越小，積越大。所以當(dāng)這兩個(gè)質(zhì)數(shù)是所以當(dāng)這兩個(gè)質(zhì)數(shù)是43和和37時(shí)，這三個(gè)數(shù)質(zhì)數(shù)的積最大。時(shí)，這三個(gè)數(shù)質(zhì)數(shù)的積最大。2433731823182 三個(gè)不同質(zhì)數(shù)的和是三個(gè)不同質(zhì)數(shù)的和是5454，這三個(gè)質(zhì)數(shù)的積最大是可能，這三個(gè)質(zhì)數(shù)的積最大是可能是（是（ ）2232913341334分解質(zhì)因數(shù)分解質(zhì)因數(shù) 把一個(gè)合數(shù)分解質(zhì)因數(shù)，就是把這個(gè)合數(shù)寫(xiě)成幾個(gè)把一個(gè)合

11、數(shù)分解質(zhì)因數(shù)，就是把這個(gè)合數(shù)寫(xiě)成幾個(gè)質(zhì)數(shù)相乘的形式，我們常用短除法分解質(zhì)因數(shù)。質(zhì)數(shù)相乘的形式，我們常用短除法分解質(zhì)因數(shù)。把把3030分解質(zhì)因數(shù)分解質(zhì)因數(shù)30被除數(shù)被除數(shù)除號(hào)除號(hào)除數(shù)除數(shù) 2除數(shù)一般除數(shù)一般用最小質(zhì)用最小質(zhì)數(shù)開(kāi)始除數(shù)開(kāi)始除起，如果起，如果2不是被不是被除數(shù)的因除數(shù)的因數(shù)，就用數(shù)，就用下一個(gè)質(zhì)下一個(gè)質(zhì)數(shù)數(shù)315商，第二次的被除數(shù)商，第二次的被除數(shù)第二第二次的次的除數(shù)除數(shù)35第二次的商（不是余數(shù)）第二次的商（不是余數(shù)）30 235把把4040、1818、3636、9191分別用短除法分解質(zhì)因數(shù)分別用短除法分解質(zhì)因數(shù)奇數(shù)偶數(shù)（奇數(shù)偶數(shù)（ ）奇數(shù)奇數(shù)（奇數(shù)奇數(shù)（ ）偶數(shù)偶數(shù)（偶數(shù)偶數(shù)（ ）奇數(shù)奇數(shù)偶數(shù)偶數(shù)偶數(shù)偶數(shù)奇數(shù)偶數(shù)（奇數(shù)偶數(shù)（ ）偶數(shù)奇數(shù)（偶數(shù)奇數(shù)（ ）奇數(shù)奇數(shù)（奇數(shù)奇數(shù)（ ）偶數(shù)偶數(shù)（偶數(shù)偶數(shù)（ ）奇數(shù)奇數(shù)偶數(shù)偶