Answer:
a. 
b. 
Step-by-step explanation:
First, we need tot find a general expression for the amount of caffeine remaining in the body after certain time. As the problem states that every hour x percent of caffeine leaves the body, we must substract that percentage from the initial quantity of caffeine, by each hour passing. That expression would be:

Then, to find the amount of caffeine metabolized per hour, we need to differentiate the previous equation. Following the differentiation rules we get:

The rate is negative as it represents the amount of caffeine leaving the body at certain time.
Area= pi x r^2
hence,
pi x r^2 = 36 x pi
=> r^2=36
=>r= root over 36 = 6
in short...the radius is 6
The etimated answer would be 20. The method that I used is I rounded 3.9 to 4 and 4.6 to 5 and then I mutiplied. Hope I helped
Answer:
<h2>y = 2.8</h2><h2>x = 14</h2>
Step-by-step explanation:
To solve an equation, we can only have one variable. In this case, we are given the system 2x = 5y + 14. However, we are given the value of x in terms of y. We can substitute 10y in for 2x and solve.
10y = 5y + 14
First, we need to get all the variables on one side of the equation, so we subtract 5y.
5y = 14
Divide by 5
y = 14/5 or 2 4/5 or 2.8
Now for the x part.
2x = x + 14
Subtract 1x
x = 14
Now we check our answer.
2(14) = 5(2.8) + 14
28 = 14 + 14
28 = 28
Because 28 equals 28, our solutions are correct.