Tutors Answer Your Questions about logarithm (FREE)
Question 150439: Ok, here is a real life equation that I need to solve for a calulation I'm doing at work. I need to solve for x in the following equation:
A = B * (1+i)^x + C * (1+j)^x
where i and j are interest rates and A, B and C are dollar amounts. In story problem language the problem is: How long will it take for Fund B and Fund C combined take to grow to amount A given that Fund B is growing at i% and Fund C is growing at j%? I know I can't just multiply both sides by ln in this equation and have it work, so I'm not sure what to do with it.
Click here to see answer by stanbon(75887)  |
Question 150694: Hello E-Instructors :)
Would someone kindly show me how to solve this problem correctly?
Problem: The level of a prescription drug in the human body over time can be found using the formula:
L= ___D___
''''''''1-(1/2)^n/H
where D is the amount taken every 'n' hours and H is the drug's half-life in hours.
(''''These marks are merely spacers and not intended to be part of the equation).
1. If 2.5 milligrams of Lorazepam with a half-life of 14 hours is taken
every 24 hours, then to what level does the drug build up over time?
So far I think that the formula may look like this:
2.5 = ___24________
'''''''''''''1-(1/2)^24/14
Then maybe this:
2.5 = ___24____
'''''''''''''0.3047534
2.5 = 69.057991
Then, I don't know what to do next or if what I've done is even close to being right. :P
2. If a doctor wants the level of Lorazepam to build up to a level
of 5.58 milligrams in a patient taking 2.5 milligram doses, then how
often should the doses be taken?
I'm completely in the dark about this one.
3. What is the difference between taking 2.5 milligram of Lorazepam
every 12 hours and taking 5 milligrams every 24 hours?
This one, I might subtract results from these two equations:
2.5 = ___12_________
''''''''''''1-(1/2)^12/14
from
5 = ___24_______
''''''''''1-(1/2)^24/14
Well, that would be after I have learned how to solve the first question
correctly. ;)
Thank you so much for sharing your valuable knowledge with a mathematically challenged damsel like myself.
Grateful,
J. ;)
Click here to see answer by edjones(8007)  |
Question 151178: Story problem: A can of soda at 79 degrees F is placed in a refrigerator that maintains a constant temperature of 36 degrees F. The temperature T of the soda t minutes after it is placed in the refrigerator is given by T(t)=36+43e^-.058t.
Part a) Find the temperature to the nearest degree of the soda 10 minutes after it is placed in the refrigerator.
I substituted 10 into the equation and got 60 degrees F. I understand this part.
Part b) When, to the nearest minute, will the temperature of the soda be 45 degrees F? HELP! I think that you need to plug in equations to graph it but I don't know what to plug in.
Thanks,
Rose
Click here to see answer by vleith(2983) |
Question 151243: In the formula A=I^ekt, A is the amount of radioactive material remaining from an initial amount I at a given time t and k is a negative constant determined by the nature of the material. An artificat is discovered at a certain site. If it has 53% of the carbon of the carbon-14 it originally contained, what is the approximate age of the artificat? (carbon-14 decays at the rate of 0.0125% annually.) Round to the nearest year.
Click here to see answer by stanbon(75887) |
Question 151244: Suppose the amount of a radioactive element remaining in a sample of 100 milligrams after x years can be described by A(x)=100e^-0.01657x. How much is remaining after 257 years. Round the answer to the nearest hundredth of a milligram.
Click here to see answer by stanbon(75887) |
Question 151246: The population growth of an animal species is described by F(t)=500+90 log3 (2t+1) where t is measured in months. Find the population of this species in an area 40 month(s) after the species is introduced.
Click here to see answer by oscargut(2103)  |
Question 151505: Example 4 on page 352 shows how to do this problem, but I am having problems factoring once I get to the point of setting the 2-x-x^2>0 and then solving for x (factoring is one of my major weaknesses). I seem to have trouble with factoring whenever I am faced with needing to combine the same variable in two different forms (e.g. the -x-x^2). Thanks.
Click here to see answer by checkley77(12844) |
Question 151505: Example 4 on page 352 shows how to do this problem, but I am having problems factoring once I get to the point of setting the 2-x-x^2>0 and then solving for x (factoring is one of my major weaknesses). I seem to have trouble with factoring whenever I am faced with needing to combine the same variable in two different forms (e.g. the -x-x^2). Thanks.
Click here to see answer by jim_thompson5910(35256) |
Question 152358: Suppose that the function P= 11+44lnx represents the percentage of inbound e-mail in the U.S. that is considered spam, where x is the number of years after 2002.
Use this model to determine in how many years it will take for the percent of spam to reach 85%?
I am having trouble trying to solve this problem.
I understand that 85=11+44lnx is how to set up the problem, but am not sure how to isolate x to find out the number of years.
Click here to see answer by ankor@dixie-net.com(22740)  |
Question 152408: Hi, my name is Stormy i'm going into 9th grade and I start Wednesday.I have no clue what the logarithm is and i would like too know so that i have a headstart in algebra concept this year. I get all a's and don't want them to drop. This is the first year i did not attend summer school and they learned the logarithm this year. if you could please give me a short explanation of what the logarithm is i would greatly appreciate it.
Thanks again,
Stormy
Click here to see answer by Earlsdon(6294) |
Question 152620: Would someone kindly help me with this algebra question?
A satellite has an elliptical orbit around the earth with one focus at the earth’s center, E. The earth’s radius is 4,000 miles. The highest point that the satellite is from the surface of the earth is 800 miles, and the lowest is 200 miles. What is the eccentricity of the satellite’s orbit?
Thank you in advance for sharing your valuable knowledge :0) !!!
Grateful,
Jai
Click here to see answer by scott8148(6628)  |
Question 152620: Would someone kindly help me with this algebra question?
A satellite has an elliptical orbit around the earth with one focus at the earth’s center, E. The earth’s radius is 4,000 miles. The highest point that the satellite is from the surface of the earth is 800 miles, and the lowest is 200 miles. What is the eccentricity of the satellite’s orbit?
Thank you in advance for sharing your valuable knowledge :0) !!!
Grateful,
Jai
Click here to see answer by Edwin McCravy(20081)  |
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