(1-1/19)*(1-1/20)*(1-1/21)*(1-1/22)*...(1-1/99)=

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(1-1/19)*(1-1/20)*(1-1/21)*(1-1/22)*...(1-1/99)=

(1-1/19)*(1-1/20)*(1-1/21)*(1-1/22)*...(1-1/99)=
(1-1/19)*(1-1/20)*(1-1/21)*(1-1/22)*...(1-1/99)=

(1-1/19)*(1-1/20)*(1-1/21)*(1-1/22)*...(1-1/99)=
原式=(18/19)*(19/20)*(20/21)*(21/22)*...*(97/98)*(98/99)
=18/99
=2/11

(1-1/19)*(1-1/20)*(1-1/21)*(1-1/22)*...(1-1/99)
=18/19×19/20×20/21×21/22×......×98/99
=18/99=2/11

(1-1/19)*(1-1/20)*(1-1/21)*(1-1/22)*...(1-1/99)
=18/19×19/20×20/21×21/22×......×98/99
=18/99
=2/11