An individual has 3 different email accounts. Most of her messages, in fact 60% come into account #1, whereas 30%come into accou
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The half life of the substance is 6.92 days.
<h3>What is the Half life ?</h3>Half life can be defined as the time required to reduce the concentration to half of its initial value.
Here the equation given is
The concentration will reduce to half therefore
so,
ln 0.5 = - 0.1001 * t(1/2)
-0.693 = -.1001 * t(1/2)
t(1/2) = 6.92 days.
Therefore the half life of the substance is 6.92 days.
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Answer:
(a) 120 choices
(b) 110 choices
Step-by-step explanation:
The number of ways in which we can select k element from a group n elements is given by:
So, the number of ways in which a student can select the 7 questions from the 10 questions is calculated as:
Then each student have 120 possible choices.
On the other hand, if a student must answer at least 3 of the first 5 questions, we have the following cases:
1. A student select 3 questions from the first 5 questions and 4 questions from the last 5 questions. It means that the number of choices is given by:
2. A student select 4 questions from the first 5 questions and 3 questions from the last 5 questions. It means that the number of choices is given by:
3. A student select 5 questions from the first 5 questions and 2 questions from the last 5 questions. It means that the number of choices is given by:
So, if a student must answer at least 3 of the first 5 questions, he/she have 110 choices. It is calculated as:
50 + 50 + 10 = 110