解：
∵1/(1×3)=1/2×(1-1/3)
1/(3×5)=1/2×(1/3-1/5)
1/(5×7)=1/2×(1/5-1/7)
1/(7×9)=1/2×(1/7-1/9)
1/(9×11)=1/2×(1/9-1/11)
∴1/(1×3)+1/(3×5)+1/(5×7)+1/(7×9)+1/(9×11)
=1/2×(1-1/3+1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11)
=1/2×10/11
=5/11
答案：5/11
33717/10395
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