六年级数学问题

1.=5又5/9+2又4/9-0.8）×（38/5×5/4+12/5+5/4）
=26/5×25/唤碧2
=65
2.＝1.1×4又21/97＋40.9×19/97－4.09×9/和族举97
＝11/10×409/97＋409/10×19/97－409/100×9/97
＝11/10×409/97＋19/10×409/97－9/100×409/97
＝409/97×（11/10＋19/穗茄10－9/100）
＝409/97×291/100
＝409×3/100
＝12.27
3.貌似除不尽。

1.(5又5/9-0.8+2又4/9)×(7.6÷4/5+2又2/5×1.25)
=7.2*（7.6+2又2/5）*1.25=7.2*10*1.25=90

2.1.1×4又21/97+40.9÷5又2/19-4.09×9/97=1.1×409/97+40.9*（19/97-0.9/97)=40.9*(11/97+18.1/97)=40.9*29.1/租橡97=12.27

3.1/21+1/77+1/165+1/285+1/437 =1/(3*7)+1/(7*11)+1/(11*15)+1/(15*19)+1/(19*23)=1/4*(1/3-1/7)+1/4*(1/7-1/11)+1/4*(1/11-1/15)+1/4*(1/15-1/19)+1/4*(1/19-1/弊大旁23)=1/4*(1/3-1/7+1/仿备7-1/11+1/11-1/15+1/15-1/19+1/19-1/23)
=1/4*(1/3-1/23)=5/69

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