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Let
A = event that the student is on the honor roll
B = event that the student has a part-time job
C = event that the student is on the honor roll and has a part-time job
We are given
P(A) = 0.40
P(B) = 0.60
P(C) = 0.22
note: P(C) = P(A and B)
We want to find out P(A|B) which is "the probability of getting event A given that we know event B is true". This is a conditional probability
P(A|B) = [P(A and B)]/P(B)
P(A|B) = P(C)/P(B)
P(A|B) = 0.22/0.6
P(A|B) = 0.3667 which is approximate
Convert this to a percentage to get roughly 36.67% and this rounds to 37%
Final Answer: 37%
<span>If the intial count was 100,000 bacteria, after one hour 90% decrease => 10 % stands => 100,000*0.1 bacetria. After two hours 90% decrease => 10% stands => 100,000*0.1^2. After three hours, they stand 100,000 * 0.1^3. After four hours, 100,000*0.1^4 and after five hours 100,000*0.1^5 = 1 bacteria. Answer: 1 bacteria. If the inital count is different you just have to muliply the inicial count time (0.1^n) to get the number of bacteria after n hours, and if the number of hours is 5, then the factor is (0.1^5). </span>
