(1-19/1)(1-20/1)(1-21/1)·

(1-19/1)(1-20/1)(1-21/1)···(1-97/1)(1-98/1)(1-99/1)

1个回答

(1-19/1)(1-20/1)(1-21/1)···(1-97/1)(1-98/1)(1-99/1)
=18/19*19/20*20/21*……*96/97*97/98*98/99
=18/99
=2/11