请教几道分数简便运算题1/(2×5) +1/(3×5)+1/(8×11)+……1/(20×23)4/3+7/12-9/20+11/30-13/421/12+1/20+1/30+1/42+1/56+1/72+1/901/(1×5) +1/(5×9)+1/(9×13)+……1/(55×59)还有一题:229又1/11除以46又1/44即2520/11除以2025/44
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请教几道分数简便运算题1/(2×5) +1/(3×5)+1/(8×11)+……1/(20×23)4/3+7/12-9/20+11/30-13/421/12+1/20+1/30+1/42+1/56+1/72+1/901/(1×5) +1/(5×9)+1/(9×13)+……1/(55×59)还有一题:229又1/11除以46又1/44即2520/11除以2025/44
请教几道分数简便运算题
1/(2×5) +1/(3×5)+1/(8×11)+……1/(20×23)
4/3+7/12-9/20+11/30-13/42
1/12+1/20+1/30+1/42+1/56+1/72+1/90
1/(1×5) +1/(5×9)+1/(9×13)+……1/(55×59)
还有一题:229又1/11除以46又1/44
即2520/11除以2025/44
请教几道分数简便运算题1/(2×5) +1/(3×5)+1/(8×11)+……1/(20×23)4/3+7/12-9/20+11/30-13/421/12+1/20+1/30+1/42+1/56+1/72+1/901/(1×5) +1/(5×9)+1/(9×13)+……1/(55×59)还有一题:229又1/11除以46又1/44即2520/11除以2025/44
1/(2×5) +1/(3×5)+1/(8×11)+……1/(20×23)?
1/(2×5)=(1/2-1/5)÷3
1/(5×8)=(1/5-1/8)÷2
1/(8×11)=(1/8-1/11)÷3
……
1/(20×23)=(1/20-1/23)÷3
1/(2×5) +1/(5×8)+1/(8×11)+……1/(20×23)
=1/3×(1/2-1/5+1/5-1/8+1/8-1/11+...+1/20-1/23)
=1/3×(1/2-1/23)
=1/3×21/16
=7/46
4/3+7/12-9/20+11/30-13/42
=1+1/3+1/3+1/4-1/4-1/5+1/5+1/6-1/6-1/7
=5/3-1/7
=32/21
1/12+1/20+1/30+1/42+1/56+1/72+1/90
=1/3×4+1/4×5+...+1/9×10
=1/3-1/4+1/4-1/5+...+1/9-1/10
=1/3-1/10
=7/30
1/1×5=(1-1/5)/4
1/5×9=(1/5-1/9)/4
1/(1×5) +1/(5×9)+1/(9×13)+……1/(55×59)
=1/4×(1-1/5+1/5-1/9+1/9-1/13+...+1/55-1/59)
=1/4×(1-1/59)
=1/4×58/59
=29/118
229又11分之1÷46又44分之1
=2520/11÷2025/44
=2520/11×44/2025
=224/45
=4又44/45