tough and tricky questions : probability . medical analysts predict that a quarter of all people who are infected by a certain biological agent could be expected to be killed for each day that passes during which they have not received an antidote . what fraction of a group of 1000 people could be expected to be killed if infected and not treated for 3 full days ?  Choose the correct choice from the following:
A) 37 / 64
B) 8 / 27
C) 2 / 3
D) 19 / 27
E) 65 / 81

Rationale: at the end of each day we will have 3 / 4 alive . so after 3 days we will have ( 3 / 4 ) ^ 3 people alive . therefore , fraction of dead people will be 1 - ( 3 / 4 ) ^ 3 = 37 / 64 . the correct answer is a .
Answer: A