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Come and help those who know the clever questions in grade six.
1/( 1×3)+ 1/(3×5)+ 1/(5×7)+……+ 1/(3 1×33)+ 1/(33×35)

= 1/2×( 1- 1/3)+ 1/2×( 1/3- 1/5)+ 1/2×( 1/5- 1/7)+……+ 1/2×( 1/3 1 - 1/33)+ 1/2×( 1/33- 1/35)

= 1/2×( 1- 1/3+ 1/3- 1/5+ 1/5- 1/7+……+ 1/3 1- 1/33+ 1/33- 1/35)

= 1/2×( 1- 1/35)

= 1/2×34/35

= 17/35