Tutors Answer Your Questions about Exponential-and-logarithmic-functions (FREE)
Question 971904: Hi,
I am trying to plot a graph of equation A(t) = 10e^-kt where k=0.03 and t is greater or equal to 0 but less than or equal to 60.
Every time I graph it on a graphics calculator, I get a linear graph but I want a graph that will show exponentially. How can I graph it to get that? What values should I set in x-axis and y-axis.
I have found a similar website to my question: http://www-rohan.sdsu.edu/~rcarrete/teaching/M-121/s07/math121/labs/lab8/q2v1.htm
So far I have done part a where I have to find value of t algebraically using natural logs
Click here to see answer by Boreal(15235)   |
Question 972013: I need help with this problem:
2^(-100x)=(0.5)^(x-4)
I know that you are suppose to have the same base on both sides of the equation to solve the problem but I can't figure out how to get the bases the same. Any help would be appreciated.
Click here to see answer by stanbon(75887) |
Question 972050: I need help with this problem:
The number of bacteria in a certain culture increased from 600 to 1800 between 7:00am and 9:00am. Assuming growth is exponential, the number of f(t) bacter1a t hours after 7:00am is given by f(t)=600(3)^(t/2).
a. Estimate the number of bacteria in the culture at 8:00am, 10:00am, and 11:00am.
b. Sketch the graph of f for 0<=t<=4.
Any help would be greatly appreciated.
Click here to see answer by Boreal(15235) |
Question 972051: I'm having a hard time with exponential functions. Here's the problem:
The radioactive bismuth isotope 210Bi has a half-life of 5 days. If there is 100 milligrams of 210Bi present at t=0, then the amount f(t) remaining after t days is given by f(t)=100(2)(^-t/5).
a. How much 210Bi remains after 5 days? 10days? 12.5 days?
b. Sketch the graph of f for 0<=t<=30.
Thank you!!
Click here to see answer by Boreal(15235) |
Question 972668: The speed of light often denoted by the variable c, is 2.998 x 10^8 meters per second. Because the distance light travels in one year is so large, in 1838 Freidrich Bessel coined the term "light year" to represent this distance. He announced that the distance to the star 61 Cygni was 10.3 light years.
Given that there are 3600 seconds in an hour, 24 hours in a day, and approximately 365.24 days in a year, what is the distance to 61 Cygni in meters? Give your answer in scientific notation with three decimal places.
Should I multiply c X 3600 X 24 X 365.24 X 10.3? That seems too simple though I am not sure exactly how to start..
Click here to see answer by Boreal(15235) |
Question 972858: The value of a car after t years can be found using the formula V = C(1 - r)t, where V is the current value of the car, C is the original price of the car, and r is the rate of depreciation.
Solve the formula for r .
Raj bought a car 4.5 years ago for $25,000, and the current value of the car is $12,000. At what percentage rate has the car depreciated? Round your answer to the nearest whole number.
Click here to see answer by Boreal(15235) |
Question 972861: If the amplitude of a large quake is 1,000 times greater than the amplitude of a smaller quake, what is the difference in their magnitudes on the Richter scale? Use the following formula to find the difference, where ML and MS represent the magnitudes of the larger and smaller quakes, respectively, and AL and AS represent the amplitudes of the larger and smaller quakes, respectively.
The formula is
ML-MS=log(AL/AS)
Click here to see answer by solver91311(24713)  |
Question 972664: You are making an arrangement with 13 cylindrical beeswax candles where all the candles are three times as tall as they are wide. If you want the 3 medium candles to be twice the height of the 9 small candles and the large candle to be three times as tall as the small candles, find the maximum height and diameter of the candles you can make from a 10 pound block of beeswax, given that one pound of beeswax has a volume of approximately 28.622 cubic inches. Round your answers to the nearest hundredth of an inch.
I know that the volume of cylinder is= pir^2h (small candles)
So are the medium candles pir^2(2h)
and the large candle pir^2(3h)
but it also says 3times as tall as they are wide so do I multiply that at the end?
Click here to see answer by ankor@dixie-net.com(22740)  |
Question 973015: A rocket of mass m = 500 kg is travelling in a straight line for a short time.
The distance in metres covered by the rocket during this time is described
by the function
s(t) = 220t-15t^2-60ln(t + 1)
where t > 0 is the time in seconds.
(a) Find a function that describes the speed of the rocket.
(b) What is the distance covered by the rocket by time t = 6 seconds?
(c) Find the value of time t when the speed of the rocket is 100 ms^-1
(d) Find a function that describes the acceleration of the rocket
(e) Find the acceleration of the rocket at t = 3 seconds.
(f) Find the time when the rocket's acceleration is -15ms^-2.
Click here to see answer by Alan3354(69443)  |
Question 973077: I need to find the inverse function to the following and am a bit overwhelmed. Is it possible to walk me through the best way to do it? I know the general steps for finding an inverse function, but am having trouble solving for x in this case.
Click here to see answer by lwsshak3(11628) |
Question 973066: How do you do this decay problem?
The radioactive isotope 123I, used in nuclear imaging, decays continuously at a rate of 5.25% per hour.
(a) Approximate the percentage remaining of any initial amount after 26.4 hours.
(b) What is the half-life of 123I?
For part a I think the formula for that is A(t)=A*e^(kt). The problem that I'm having with this is that I don't know the initial amount (A). Here are the variables:
A=?
k=?
t=26.4
It seems like it's asking what (k) would be but I don't know how to solve for (k) without knowing the initial amount (A). I think I may be looking at it wrong. Any help on this one would be appreciated. I know how to do part b but I need to know how to do part a first before I can do b.
Thank you!!
Click here to see answer by josgarithmetic(39620) |
Question 973363: What is/are the solution(s) to 3^(x+1)+8=3^(1-x) ?
How did you solve for it?
A similar problem is: e^(2x-1)=3 What is x? This one involves logarithms and the answer contains ln although i don't know what that quite means.
Also, what is the value of x in this problem:
sqrt(x- sqrt(x- sqrt(x... =6
what is x?
The website couldn't proccess the equation using the formula plotting system, sorry.
The square roots are inside each other and it goes on indefinitely but I dont get how the sum is 6
Click here to see answer by stanbon(75887) |
Question 973696: Suppose a certain population increases by 20% every ten years. By what percent does the population increase each year (assuming a constant growth rate)? (Hint: the answer is not 2%.)
Show your work. Round to the nearest hundredth of a percent.
I believe they are asking for me to use the equation A = Pe^(rt)
Thank you!!
Click here to see answer by josgarithmetic(39620) |
Question 973881: Suppose a certain population increases by 20% every ten years. By what percent does the population increase each year (assuming a constant growth rate)? (Hint: the answer is not 2%.)
Show your work. Round to the nearest hundredth of a percent.
I believe they are asking for me to use the equation A = Pe^(rt)
Thank you!!
Click here to see answer by Boreal(15235) |
Question 973878: Suppose a certain population increases by 20% every ten years. By what percent does the population increase each year (assuming a constant growth rate)? (Hint: the answer is not 2%.)
Show your work. Round to the nearest hundredth of a percent.
Thank you!!
Click here to see answer by josgarithmetic(39620) |
Question 973861: Suppose a certain population increases by 20% every ten years. By what percent does the population increase each year (assuming a constant growth rate)? (Hint: the answer is not 2%.)
Show your work. Round to the nearest hundredth of a percent.
I believe they are asking for me to use the equation A = Pe^(rt)
Thank you!!
Click here to see answer by josgarithmetic(39620) |
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