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.
Adults = 9
Children = 2
Let x be the number of adults.
11-x is the number of children.
22x + 15(11-x) = 228
22x + 165 - 15x = 228
22x - 15x = 228 - 165
7x = 63
7x / 7 = 63 / 7
x = 9 number of adults.
11 - x = 11 - 9 = 2 number of children.
To check:
22x + 15(11-x) = 228
22(9) + 15(11-9) = 228
198 + 30 = 228
228 = 228
(not my answer btw)
Answer:
The sample would double in 9 hours
Step-by-step explanation
The number of hours it will take for the sample to double can be found using the 72 rule.
The 72 rule is such that a growth rate would double itself by it is used in dividing the number 72 as shown below:
number of hours =72/8=9 hours
The number of hours it would take the sample to double is 9 hours as computed above.
Answer:
Step-by-step explanation:
1. Combine Like Terms
24 + 6a = 6 - 4a
+4a +4a
24 + 10a = 6
-24 -24
10a = -18
___ ___
10 10
a= -1.8
The answer to the question is 215