Tough and Tricky questions: Probability.
Medical analysts predict that half 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 1,000 people could be expected to be killed if infected and not treated for three full days? Choose the correct choice from the following:
A) 16/81
B) 7/8
C) 2/3
D) 19/27
E) 65/81
At the end of each day we will have 1/2 alive. So after 3 days we will have (1/2)^3 people alive. Therefore, fraction of dead people will be 1-(1/2)^3=7/8.   The correct answer is 7/8.
<result>B</result>
Tough and Tricky questions: Probability.
Medical analysts predict that half 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 1,000 people could be expected to be killed if infected and not treated for three full days?