七 整数四则混合运算【试一试·70页】 50+120÷6×5=150+20×5=150+100=250【练一练·71页】1.运算顺序:先算乘除,再算减法 先算除法,再算加减法240÷6-2×17 31-35÷3+25=40-34 =51-12+25=6 =642.两题都不对。 440-200÷5×8 110-20×5+25=440-40X8 =110-100+25=440-320 =10+25=120 =35【练一练·71页】运算顺序:先算小括号里面的乘法,再算小括号里面的加法,最后算除法先算小括号里面的除法,再算小括号里面的减法,最好算乘法(37+29×3)÷4 58×(20-78÷13)=(37+87)÷4 =58×(20-6)=124÷4 =58×14=31 =812【练习十一·72页】1. 80+2+76÷4 45-20×6÷5 28+84÷7-13=40+19 =45-24 =28+12-13=59 =21 =272. 25×30+25×20 25×(30+20)=750+500 =25×50=1250 =1250 840÷40-400÷40 (840-400)÷40=21-10 =440÷40=11 =113.72÷3-85÷5=24-17=7(平方米)答:兵兵家的人居面积比乐乐家大7平方米。4. 18×2+18+6=36+18+6=60(人)答:合唱组有60人。5. 600÷10+120÷6 26+14×70-30=60+20 =26+980-30=80 =1006-30 =976 600÷(10+120÷6) 26+14×(70-30)=600÷(10+20) =26+14×40=600÷30 =26+560=20 =586 (600÷10+120)÷6 (26+14)×(70-30)=(60+120)÷6 =40×40=180÷6 =1600=306. 25×(22+576÷32) (75+49)÷(75-44)=25×(22+18) =124 ÷31=25×40 =4=1000 6×58-(74+89) 540÷(30×15÷50)=348-163 =540÷(450÷50)=185 =540÷9 =607. 140×2+50+140=280+50+140=470(千克)答:这一天一共运进菠萝470千克。8.16×4=64 450÷50=9 2×32=6470÷5=14 3×60 |