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
问题描述：
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
答
1/(2×5) +1/(3×5)+1/(8×11)+……1/(20×23)?1/(2×5)=（1/2-1/5）÷31/(5×8)=（1/5-1/8）÷21/(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...