沪教小学数学四下2.22小数加减法的应用

沪教小学数学四下2.22小数加减法的应用

小数加减法的应用 25.2 - 8.8 - 4.2 25.2 - 8.8 - 4.2 = 25.2 – 4.2 – 8.8 = 21 – 8.8 = 12.2 ( 米 ) 25.2 - 8.8 - 4.2 = 25.2 – ( 8.8 + 4.2 ) = 25.2 – 13 = 12.2 ( 米 ) 3.5 - 1.25 - 1.5 =3.5 - 1.5 - 1.25 =2 - 1.25 =0.75 ( 升 ) 3.5 - 1.25 - 1.5 = 2.25 - 1.5 = 0.75 ( 升 ) 3.5 - 1.25 - 1.5 = 3.5 – (1.25 + 1.5) = 3.5 – 2.75 = 0.75 ( 升 ) 王大伯要耕一块 950 平方米的地，第一天耕了 274.8 平方米，第二天耕了 485.2 平方米，再耕多少平方米的地就可以耕完？ 有三箱货物，第一箱重 75.8 千克，比第二箱重 9.2 千克，第三箱货物的重量比第二箱轻 0.8 千克，第三箱中多少千克 950 - 274.8 - 485.2 = 950 - （ 274.8 + 485.2 ） = 950 - 760 = 190 （平方米） 950 - 274.8 - 485.2 = 950 - 274.8 - 485.2 = 675.2 - 485.2 = 190 （平方米） 75.8 - 9.2 - 0.8 75.8 - 9.2 - 0.8 = 75.8 – 0.8 – 9.2 = 75 – 9.2 = 65.8 ( 千克 ) = 75.8 – ( 9.2 + 0.8 ) = 75.8 – 10 = 65.8 ( 千克 ) = ( 9.3 + 9.7 )+( 9.8 + 9.2 )+( 9 + 8.8 ) = 19 + 19 + 17.8 = 38 + 17.8 = 55.8 = 9× 6 9+0.3 9+0.7 9+0.8 9- 0.2 9+0.2 +0.3+0.7+0.8-0.2+0.2 = 54 + ( 0.3 + 0.7 ) + ( 0.8 + 0.2 )-0.2 = 54 + 1+1-0.2 = 56-0.2 = 55.8 = 54+( 0.3 + 0.7 )+ 0.8 = 54+1+ 0.8 = 55+ 0.8 = 55.8 = ( 9.4 + 9.6 )+( 9.7 + 8.3 )+( 9 .4+ 9.2 ) = 19 + 18 + 18.6 = 37 + 18.6 = 55.6 = 9× 6 9+0.6 9+0.7 9+0.4 9- 0.7 9+0.2 +0.4+0.6+0.7+0.4-0.7+0.2 = 54 + ( 0.4 + 0.6 ) + ( 0.7 + 0.4 + 0.2 )-0.7 = 54 + 1+1.3-0.7 = 56.3-0.7 = 55.6 = 54+( 0.4 + 0.6 )+ 0.4+0.2 = 54+1+ 0.6 = 55+ 0.6 = 55.6 9+0.4 = 55.7-( 9.1 + 8.9 )-( 9.4 + 9.6 )-9.2 = 55.7- 18- 19-9.2 = 33.7- 19- 9.2 = 18.7- 9.2 = 9.5 = 55.7- 5×9 9+0.1 9+0.4 9+0.2 9-0.1 9+0.6 - 0.1 - 0.4 - 0.2 + 0.1 - 0.6 = 55.7- 45- 0.1 - 0.4- 0.2+ 0.1- 0.6 = 10.7- ( 0.4 + 0.6 )- ( 0.1 + 0.2 )+ 0.1 = 10.7- 1 - 0.3 + 0.1 = 9.7 - 0.3 + 0.1 = 9.4+ 0.1 = 9.5 = 10.7- ( 0.4 + 0.6 )- 0.2 = 10.7- 1 - 0.2 = 9.7 - 0.2 = 9.5