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7*15分之8-35分之12+63分之16-99分之20简便计算

解:依题意得算式, 7×15分之8-7×35分之12+7×63分之16-99分之20×7 =(15分之8-35分之12+63分之16-99分之20)×7 =【(3分之1+5分之1)-(5分之1+7分之1)+(7分之1+9分之1)-(9分之1+11分之1)】×7 =(3分之1+5分之1-5分之1-7分之1+7分之1+9分之...

7*8/15-7*12/35+7*16/63-20/99*7 = 7*[1/3+1/5-(1/5+1/7)+1/7+1/9-(1/9+1/11)] =7*(1/3-1/11)=7*8/33 =56/33

7×8/15-7×12/35+7×16/63-7×20/99 =7×(8/15-12/35+16/63-20/99) =7×(1/3+1/5-1/5-1/7+1/7+1/9-1/9-1/11) =7×(1/3-1/11) =7×8/33 =56/33 =1又23/33

4/3-8/15+12/35-16/63+20/99 =(4/3-16/63)+(12/35-8/15)+20/99 =(81/63-16/63)+(36/105-56/105)+20/99 =65/63-20/105+20/99 =65/63-12/63+20/99 =53/63+20/99 =583/693+140/693 =723/693

9×1-4/3+8/15-12/35+63 =9+63-20/15+8/15-12/35 =72-12/15-12/35 =72-4/5-12/35 =72-28/35-12/35 =72-40/35 =72-1-1/7 =71-1/7 =70又6/7

这个还真的不想去算的啊

裂项法: 8×8/15-8×12/35+8×16/63-8×20/99 =8×(8/15-12/35+16/63-20/99) =8×(1/3+1/5-1/5-1/7+1/7+1/9-1/9-1/11) =8×(1/3-1/11) =8×8/33 =64/33 =1又31/33

5/6-8/15+12/35-16/63+20/99 =1/2+1/3-1/3-1/5+1/5+1/7-1/7-1/9+1/9+1/11 =1/2+1/11 =13/22

8又2/3-7又8/15 =8+2/3-7-8/15 =1+10/15-8/15 =1又2/15 6又12/35-5又16/63 =6+12/35-5-16/63 =1+108/315-80/315 =1+28/315 =1+4/45 =1又4/45 4又20/99-3又24/143 =4+20/99-3-24/143 =1+260/1287-216/1287 =1+44/1287 =1+4/117 =1又4/117

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