第五单元 分数四则混合运算分数四则混合运算1. 5/8 7/12 10/7 1/72. 11/9 1/30 1/23. 42×(1/6+1/7) 2/3×1/4+2/3÷4 8/9×2/5+8/9×3/5= 42×1/6+42×1/7 =2/3×1/4+2/3×1/4 =8/9×(2/5+3/5)= 7+6 = (2/3+2/3)×1/4 = 8/9×1= 13 = 4/3×1/4 = 8/9 = 1/3 11/8-(5/16×6/5+2/7) 2/9÷1/5+7/9÷1/5 (28-7/8)×1/7=11/8-(3/8+2/7) =(2/9+7/9)÷1/5 =28×1/7-7/8×1/7=11/8-3/8-2/7 = 1÷1/5 =4-1/8=1-2/7 = 5 =31/8=5/7 4. (1)略 (2)120×3/5×2/3=48(人)5. 8-8×1/4-1/4=6-1/4=23/4(米)练习七1. 3/2 2/7 20 1/2 3/8 1/6 15/2 02.(1)10×4/5×5/8=5(吨) (2)36×2/3×3/4=18(个)3.(75+65)×6/7=120(千米)4. 6/5-3×1/4=9/20(升)5.(2/3+4/5)×3/4=11/10(吨)6. x=3/10 x=3/5 x=507. 7/13×2/5-2/13×2/5 24-24×18/19 5/7÷1/4+5/7÷3/4=(7/13-2/13)×2/5 =24-(1-18/19) =5/7×4+7/5×4/3= 5/13×2/5 =24-1/19 =5/7×(4+4/3)= 2/13 =24/19 =5/7×16/3 =80/218. 3/4×7/8÷2=21/64(平方米) (1/2+4/5)×5/8÷2=13/32(平方米)9. 6×2/5÷3/20=16(千米)10. 90×(1/3+2/5)=66(个)稍复杂的分数实际问题(1)1. 1/24 11/21 1/8 2/52. 画图略,60×(1-3/5)=60×2/5=24(名)3. 168×(1-7/12)=168×5/12 =70(件)4.(1)7/8×3/4=21/32(米) (2)7/8×(1-3/4)=7/8×1/4=7/3(米) (3)7/8-3/4=1/8(米)5. 720×(5/8-1/2)=720×1/8=90(千米)稍复杂的分数实际问题(2)1. 线段图略(1)32×(1+1/8)=36(千克)(2)48×(1-1/6)=40(吨)2.(1)去年植树量 今年计划比去年多的植树量 (2)原价 降价的价格3. 8×(1+17/40)=57/5(千米)4. 2400×(1+1/4)=3000(平方千米)5. 5×6÷(5×2/5)=30÷2=15(次)稍复杂的分数实际问题(3)1. 5/6 9 25 1/252. 19/24 1/18 5/33. 48×(1+1/4)=60(棵) 1 |