文档介绍：人教版四年级数学单位:争胜小学执教者:于学勇 12×30= 25×4=125 ×8= 15×2=24×40= 18×20= 24= ()×() 30= ()×() 15= ()×() 3 100 1000 960 360 360 54656 30商店有 5盒手电筒,每盒 12个。每个手电筒卖 6元,一共可以卖多少元? 说一说,你能想到几种解法: 6 ×12 ×56 ×(12 ×5) = 这样的算式真有趣, 怎么算结果都一样!你还能举些例子吗? 24 ×2×5 32 × 125 × 25 =24 ×(2 ×5) =24 ×10 =240 = (4 ×8)×125 ×25 = (4 ×25)×(8×125 ) =100 ×1000 =100000 19×6×5 27×4×5 =27 ×(4×5) =27 ×20 =540 =19 ×(6×5) =19 ×30 =570 15× 12 =15 ×(4 ×3) = (15×4)×3 =60 ×3 =180 35×18 25×36 =25 ×(4 ×9) = (25×4)×9 =100 ×9 =900 =35 ×(2 ×9) = (35×2)×9 =70 ×9 =630 25×14 =25×10×4=250 ×4 =1000 4×5×19 =4×(5×19) =4×95 =380 不 OK 不 OK 1、与 6×19 ×2相等的式子是( ) ①6÷ 2 ×19 ② 6 ×2 ×19 ③ 9 ×6 ×2 2、15 ×5 ×4用简便方法计算是( ) ①15×(5×4)②15×4×5 ③4 ×(5×15) 3、125 ×72用简便方法计算是( ) ①125 ×4×18 ②125 ×2×36 ③125 ×8 ×9 ②①③ 49×4×537×25 ×456 ×125 25×4×925×2×5 37×(25 ×4)25×(2×5)7×(8×125 )49×(4×5)25×9×4 12× 2× 5 =12 ×(2×5) 22× 6× 5 =22 ×(6×5) 35× 14 =35 ×(2×7) 22× 25 =11 ×(2×25) 45× 2× 9 =90 ×9 55× 12 =55 ×2 ×6√√√√× √