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Mathematics 7 Online
OpenStudy (anonymous):

Eric made a $4500 purchase on his credit card that has an annual interest rate of 13% which compounds continuously. If he did not make a payment for an entire year, how much does he owe? Round your answer to two decimal places

OpenStudy (anonymous):

????????

OpenStudy (anonymous):

@CO_oLBoY

OpenStudy (radar):

Use the formula for continuous compounding of interest.\[A = Pe ^{rt}\]

OpenStudy (radar):

To use this formula substitute the original amount ($4500) for P, e is a constant and is the base for natural logs. The exponents are r which is the interest rate (13% or .13) and t is the amount of years in your case just 1. Plug those values and solve.

OpenStudy (anonymous):

divide?

OpenStudy (anonymous):

@radar

OpenStudy (anonymous):

585?

OpenStudy (radar):

There is no dividing mostly multiplying rt is .13 times 1 or .13 it would look like this\[A = 4500e ^{.13}\]

OpenStudy (anonymous):

so 4500 times 13?

OpenStudy (anonymous):

346.15?

OpenStudy (radar):

No it is 4500 times e to the .13 power. You will need to use your calculator. e = 2.71828. \[A=4500\times 2.71828^{.13}\]

OpenStudy (anonymous):

2.71828 to the 13 is 35.33764

OpenStudy (radar):

That is .13 there is a decimal point just to the left of the 1 in .13 (13%)

OpenStudy (anonymous):

i mean .13

OpenStudy (anonymous):

thats the answer I got 35.33764

OpenStudy (radar):

I get the value for \[2.71828^{.13}=1.138828284\]

OpenStudy (anonymous):

ok is 1.138828284 the answer

OpenStudy (radar):

It is obviously going to be less than 4 and much less than 35.

OpenStudy (anonymous):

would it be rounded like this 1.139?

OpenStudy (radar):

No multiply that by $4500.

OpenStudy (anonymous):

multiply 1.138828284 by 4500?

OpenStudy (radar):

That means his original debt of $4500 has now increased to $5124.727 or about 625 dollars of interest in one year no less!!

OpenStudy (radar):

yes multiply.

OpenStudy (anonymous):

5,124.72726?

OpenStudy (radar):

Yes, gain confidence through practice.

OpenStudy (anonymous):

is that what its rounded too?

OpenStudy (anonymous):

or is it 5,124.73?

OpenStudy (radar):

Round it to cents, that looks good to me.

OpenStudy (anonymous):

ok good

OpenStudy (radar):

In compound interest you will eventually be working with natural logs.

OpenStudy (anonymous):

can you help me with another?

OpenStudy (radar):

I don't know until I see it, I am not infallible.

OpenStudy (anonymous):

A colony of bacteria grows at an exponential rate according to the function P(t) = 2250e^0.11t which describes the number of bacteria P at time t (in hours). Find the following: (A) Find the number of bacteria at t = 0 hours. number of bacteria = (B) Find the growth rate of the colony. Round your answer to two decimal places. growth rate = (C) Find the population after 10 hours. population = (D) When will the population double? Round your answer to one decimal place. time = hours (E) At what time will the population reach 7000? Round your answer to one decimal place. time = hours

OpenStudy (anonymous):

lol ok me neither this stuff is so confusing!

OpenStudy (radar):

Well that is quite a problem. First do know how to use logs?

OpenStudy (anonymous):

no I dont

OpenStudy (radar):

I am surprised you would be expected to know how to solve these,,,,,,unless you are good at using the functions on your calculator. Are you adept at using your calculator?

OpenStudy (anonymous):

yea i have an online algebra calculator

OpenStudy (radar):

O.K Lets try the first part I want to be sure I have the correct function for that bacteria>\[P(t)=2250e ^{0.11t}\]. Is that correct?

OpenStudy (anonymous):

ok hold on

OpenStudy (anonymous):

it wants to know if I should factor it or find the symmetry

OpenStudy (anonymous):

or all these other options?

OpenStudy (radar):

That is saying the population of the bacteria as a function of time (t) is that equation. A. Population at time 0 (t=0). That one is easy because e to the 0 power is one 1 as is anything to the 0 power is, so the population initially is 2250 bacteria, but as time goes by it will grow according to the equation provided in the problem. For part A you will not need to factor or seek symmetry.

OpenStudy (anonymous):

ok then It wont give me a topic

OpenStudy (anonymous):

so I cant use the calculator

OpenStudy (radar):

Yes, and did you understand the solution for Part A.??

OpenStudy (anonymous):

not really

OpenStudy (anonymous):

2250 divide into 0.11

OpenStudy (radar):

If t=0 what is 0.11times 0 is what?

OpenStudy (anonymous):

0.11

OpenStudy (radar):

No! anything times 0 is 0

OpenStudy (radar):

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