✔ 最佳答案
According to the results of past years,the probability that a f.5 student of modern secondary school passes 5 or more subjects in the HKCEE is 0.99 .if 200 students in that school attend HKCEE this year,estimate the number of students who will pass 5 or more subjects.
the number of students who will pass 5 or more subjects
=200*0.99
=198
(A)What is the expected frequency of getting "6" ; in tossing a fair dice 15 times?
the expected frequency
=15*1/6
=2.5
(B)how many times should we toss a fair dice if we expect to get "6" ; 10 times?
The number we need
=10/0.6
=60
3 . the probability that a child has taken measles by the age of 12 is 0.6 . if a teacher of a school expects that 58 students aged 12 in her school have not had measles,how many students in her school are 12 years old?
the probability that a child has not taken measles by the age of 12
=1-0.6
=0.4
since 58 students aged 12 in her school have not had measles
the number of students in her school are 12 years old
=58/0.4
=232
