2022四年級(jí)數(shù)學(xué)下冊(cè)第1單元小數(shù)的意義和加減法第1招巧算小數(shù)加減法課件北師大版

1、第1招 巧算小數(shù)加減法BS 四年級(jí)下冊(cè) 用簡(jiǎn)便方法計(jì)算：7.136.966.917.2270.13算式中的四個(gè)數(shù)都與整數(shù)7比較接近，所以將7作為基準(zhǔn)數(shù)經(jīng)典例題70.0470.0970.22 7.136.966.917.22(70.13)(70.04)(70.09)(70.22)74(0.130.040.090.22)280.2228.22規(guī)范解答：13提示：點(diǎn)擊 進(jìn)入題組訓(xùn)練運(yùn)用加法運(yùn)算律簡(jiǎn)算運(yùn)用減法的性質(zhì)簡(jiǎn)算運(yùn)用湊整法簡(jiǎn)算運(yùn)用基準(zhǔn)數(shù)法簡(jiǎn)算2456789101112運(yùn)用配對(duì)求和法簡(jiǎn)算104.614.61簡(jiǎn)算。(1)5.264.64.74運(yùn)用加法運(yùn)算律簡(jiǎn)算技 巧 15.264.744.6加法交換

2、律2. 2.66.923.40.08(2.63.4)(6.920.08)6713加法分配律3 11.34(7.342.25)11.347.342.25運(yùn)用減法的性質(zhì)簡(jiǎn)算技 巧 242.251.7542.37(2.41.63)2.371.632.442.41.62.372.41.63運(yùn)用湊整法簡(jiǎn)算技 巧 35 33.2819.4116.6220.5933.2816.62(19.4120.59)33.2816.6219.4120.5949.9409.96 3.561.722.443.562.441.7261.724.28運(yùn)用基準(zhǔn)數(shù)法簡(jiǎn)算技 巧 47. 0.90.990.9990.99991111(

3、0.10.010.0010.0001)(10.1)(10.01)(10.001)(10.0001)40.11113.8889以1為基準(zhǔn)8. 9.69.79.89.910101010(0.40.30.20.1)(100.4)(100.3)(100.2)(100.1)40139以10為基準(zhǔn)9 10.0210.19.889.751040.120.020.10.25(100.12)(100.02)(100.1)(100.25)400.2539.75以10為基準(zhǔn)10. 15.414.614.815.315.71550.40.40.20.30.7(100.4)(150.4)(150.2)(150.3)(150.7)750.875.8以15為基準(zhǔn)運(yùn)用配對(duì)求和法簡(jiǎn)算技 巧 511. 1.21.41.61.83.63.8 項(xiàng)數(shù)(3.81.2)0.2114等差數(shù)列求和公式：(首項(xiàng)末項(xiàng))項(xiàng)數(shù)2原式(1.23.8)142 35項(xiàng)數(shù)=(末項(xiàng)首項(xiàng))公差+1 12. 0.10.30.59.79.9項(xiàng)數(shù) (9.90.