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#76 Re: Help Me ! » rate of growth/decay in exponential function » 2021-12-13 13:45:52
yes what is that gradient value of -k?
what you mean when it's decreasing rate what you mean you mean it become for example -5 % then -4% then -3%
is it in that function decreasing and getting horizontal like that? or how, is it a constant value decreasing rate for example -50%
and what is value of k represented in that mentioned function is it rate of the medicine in the blood of patient being decreased
or it's the rate of change in the saturation level will get to its end, or what is it I I know S meaning saturation level and t mean time but what is k represent in that example
#77 Help Me ! » rate of growth/decay in exponential function » 2021-12-12 17:24:36
- Hannibal lecter
- Replies: 17
Hi, please see this example talking about converting exponential function form from
into form
it's easy and understandable as you see in the following picture :-
as you can see the growth rate here is (1 - 1.65= 65%) and it's increasing rate because 1.65 > 1
and in the other function is (1-0.819 = 18.1%) and it's decreasing rate because 0 < 0.819 < 1
and I tested them all,
my problem is I found another function I wonder if I can convert it like the others too and the function is because I'm unable to find the rate while I convert it to the classic form (without e) :-
lets say k=1,t≥0
I want to convert it too so I can see the initial value and the growth rate
I just want to convert it because I want to compare between growth/decay in the form of
the reason that I want to convert it to classic form because in the book as highlighted in yellow "..the quantity increases at a decreasing rate"
again directly it said "This is realistic because as the quantity of the drug in the body increases, so does the rate at which
the body excretes the drug..."
so now I'm confused! once it say the rate is decreasing and again it said the rate is increasing, I want to know the rate in the classic form to check it by myself if it's decreasing or if it's not ( I mean the rate change not the function)
also it's strange equation it's without initial value!
I tried to convert it with my own way like this :
by assuming t is 1 and k is 1 too
so it's :-
but here when finding the rate is (1 - 0.367879441171 = 0.63212055882) and it's mean 63.2%
first it's not like k I chosed k = 1 it has to be 1%!! I choses it myself
second it's not a correct rate it has to be around 36.7% because when I try these values with the two forms of this functions it's identical
but in 63% rate it's not correct,
and this is my another problem question why this time I minus (1-0.367879441171) the rate is wrong? I minus 1 always as you can see above and it's correct why this time in this function is not correct
#78 Help Me ! » why subtract this kinky number is equal 1 » 2021-12-12 14:52:12
- Hannibal lecter
- Replies: 5
hi, why 1 - 1.928749848×10^(-22) equal = 1 in online calculators?
I used also google calculator :-
I tried to remove the 1 integer to become 0.928749848×10^(-22)
but still the same the sum equal 1! is there something wrong?
...
...
#79 Re: Maths Is Fun - Suggestions and Comments » advanced search option » 2021-12-12 05:09:21
You can adjust the number of pages that are shown at once in your profile. Does that work?
Bob
it's not working for my posts option but no problem I found the post because I don't have much posts
but do you think the site can upgrade to become more advanced or the site owner are busy and not there to think about how to upgrade it
#80 Help Me ! » solving two equation » 2021-12-11 11:24:01
- Hannibal lecter
- Replies: 1
if f(1) = 250*a = 150
f(4) = 250* a^2 = 90
solving the equation to find a
I found similar question on a book I study from an example above in the picture :
but I made my own example with simple number to make it easy to illustrate
my problem and my question is how cold he dividing the two equations ( in my example and in the book example)
what thing gives to him the mechanism to do that to find the missing "a"
I mean they are two separate equation and lets say the f(1) is mean the time in first hour, and f(4) is the time of fourth hour
so they are different so what rules he lean on it to do such thing to solve this equation by dividing the two of them by themselves
note that I create my example from the book source itself (the answer is 0.59999 which men 60% percent I know the answer for the example I made but the answer is coming out like a magic I want to understand the concept of dividing two equations togather) :
#81 Help Me ! » basic algebra "multiplication" » 2021-12-11 10:33:46
- Hannibal lecter
- Replies: 1
hi,
what happen when we multiply decimal by a percentage and it is different from the concept of regular multiplication numbers concept
for example
multiply 3 * 4 is 3 + 3 + 3 + 3 = 12 or 4+4+4 = 12
the clearest explanation of this simply mean 4 copies of 3 added togather or 3 copies of 4
but
when we multiply
100 * 50% it's clearly mean 100 * 50/100 = 100
what is the deep explanation of that mean?
#82 Re: Help Me ! » converting a decimal value into a percent method » 2021-12-11 04:09:42
It's worth using this method, especially if you have a lot of calculation involving the same % increase.
Bob
I completely now understand the methods and everything about that multiplier
can you please see this following photo (I highlighted the number in red lines) :-
posted image
the book called this multiplier a growth factor! as you can see,
so is that multiplier the same as exponent? or what is it called
is it right to called it a growth factor
and thanks
#83 Re: Help Me ! » converting a decimal value into a percent method » 2021-12-10 12:30:21
hi
13.290 M / 12.853 M = 1.034
You are wondering how they got the correct percentage from this.
So an easy way to get the % increase from is just to take off the 1 (= 12.853/12.853)
In situations like these taking off the 1 will always work as 1 is the same as 100% which is the original amount before the increase.
Bob
from this screenshot I'll post in the following please if you may see it I highlighted the value by red color :
so is the number 1 + 0.034 = (1.034) called a growth factor or constant of growth or the exponent? but the exponent is ≈ 2.718?!!?
and why the book used this way? not this regular law the we always use to find percentage increase { [amount of increase] / [original amount] times 100%) }
, to illustrate the meaning of 1.034??
#84 Maths Is Fun - Suggestions and Comments » advanced search option » 2021-12-10 12:02:33
- Hannibal lecter
- Replies: 2
Hello,
when I search in my " all posts " history like this :
it show me this :
it's numbered by (page 1,page 2... etc)
can you add there additional option to view all the pages at once! to make search on posts easier and more functionality
#85 Re: Maths Is Fun - Suggestions and Comments » complex site » 2021-12-08 17:15:04
Have you tried to learn LaTex? http://www.mathisfunforum.com/viewtopic.php?id=4397
Bob
they are not working
look please :
<\frac{1}{k}>
is still the same on my screen didn't changed
#86 Help Me ! » inversely proportional » 2021-12-08 17:05:08
- Hannibal lecter
- Replies: 1
A formula representing the statement “q is inversely proportional to the cube root of p and has a positive constant
of proportionality.
the answer was
but I thought the answer would be :-
q = 1/k * p^(1/3)
k is the constant
in book manual solution from where he got the "8" number?
#87 Re: Help Me ! » percentage growth vs actual growth meaning » 2021-12-08 11:20:15
hi Hannibal lecter
Part (a) asks about the percentage growth being positive. This is 2005 to 2006. You have understood that ok.
Part (b) asks about the actual price. That is where my extra row helps. Using my 'index' of 100 as the starting point you can see the price drops in 2004. But after that the price recovers and is above 100 for the rest of the years. So I think the answer to part (b) is 2005 to 2008.
Hope that helps,
Bob
you worked it very accurate and neat I like they way you work
do you think the book needed only intervals for each consecutive years because that it's ignored some values?
pls read the book full manual solution :
(a) The largest time interval was 2004–2006 since the percentage growth rate increased from −5.7 in 2004 to 9.7 in
2006. This means that from 2004 to 2006 the US price per watt of a solar panel grew relatively more with each
successive year.
(b) The largest time interval was 2005–2006 since the percentage growth rates were positive for each of these two
consecutive years. This means that the US price per watt of a solar panel steadily increased during the two year span
from 2005 to 2006, then decreased in 2007.
do you notice about "consecutive years"? I think the BookManual solution provider understand what the textbook wanted and he give it to him right?
because from what I see now both you and other answer looks acceptable expect your answer is more accurate
#88 Help Me ! » proportionality » 2021-12-08 10:57:20
- Hannibal lecter
- Replies: 1
Hi,
y = 2x + 1
the y is not directly proportional with x because the function is not like that : y=kx
because of number +1
my question is how this number "+1+ effected on these quantity that made them not proportional to each other
my second question is : I saw this image in mathIsFun site talking about proportions (https://www.mathsisfun.com/algebra/proportions.html)
from this image I can see the white dog head is 10 and the other brown dog head is 15
also the body of white dog is 20 and body of brown dog is 30 => 10/20 = 15/30
how cold they become equal?
how can I make these quantities equal and right "=" between them
I read a lot of that and it's useful to solve some problems like finding the percent... etc
but I still can't imagine how they are equal and how could we right "equality" between them
I mean look they are different sizes
I know if I multiply the two quantity by 2 for example they will get larger is equal the head will become 20 and the other head will become 30, it's like ratio between them, but I still can not imagine how can I write equal sign between them because one is bigger from another
#89 Re: Introductions » Hello please need help from math experts very necessary topic » 2021-12-08 05:16:45
thank you for the support
#90 Re: Help Me ! » percentage growth vs actual growth meaning » 2021-12-08 05:14:44
if I didn't understand this exercise 100% is that will effect on studying the next topic which is exponential functions
if I understand this 85% can I cross and go to another topic? the next topic will talk about exponential functions
can I start reading it or I have to complete these exercises and understand it 100% from all ways?
#91 Introductions » Hello please need help from math experts very necessary topic » 2021-12-07 05:15:10
- Hannibal lecter
- Replies: 4
Hello, If someone is ignorance and not smart enough and learning math very slow
should he leave learning math or should he keep going even if it slow?
because for example study a math book of 800 pages costs me 3 months
it's 3 months mines from my age it's a lot only 1 book should I change me dreams or should I keep going and do what I'm thinking about?
please tell me the truth without motivational speeches just say to me the truth I won't feel upset
#92 Re: Help Me ! » percentage growth vs actual growth meaning » 2021-12-07 05:11:35
You'd have to wait until the end of the year before you had all the data for that year so, thinking about it some more, the 2007 point is actually 31st December 2007.
Bob
I understand you completely and you helped me a lot in that specially when you told me about negative and positive growth
but there is still a problem in the question please check that another problem with same answers and you will notice the conflict
Solar panels are arrays of photovoltaic cells that convert
solar radiation into electricity. The table shows the annual percent change in the US price per watt of a solar
panel :
a)Find the largest time interval over which the percentage growth in the US price per watt of a solar panel
was an increasing function of time. Interpret what
increasing means, practically speaking, in this case.
(b) Find the largest time interval over which the actual
price per watt of a solar panel was an increasing
function of time. Interpret what increasing means,
practically speaking, in this case.
please see the "a" branch is completely clear and the book answer is clear, the answer is from (2004-2006)
the problem again is in the actual graph, the book solution is : 2005-2006
you told me to chose the positive growth intervals right? look I draw it on notebook and you can see there is positive interval that the book ignored please see my pictures :-
there is positive interval I highlighted it in blue pen, please tell me what is happening is the book wrong or I'm not good enough to understand great ideas like this one
now because I'm confused I have to re-ask my question what is the different between growth in branch "a" and growth in branch "b" I didn't see in webs something called " actual growth I searched a lot" do you have simple example in clear numbers because I understand most of such subjects in interactive way like (price in 2011 per watt for solar panel is 2$ after growth 30% it become $2.6... and so on I only understand it this way sometimes when things goes difficult when I see numbers become real things and represent real simple things in detailed I understand more,)
so I wish after you help me in this question and we done from it I wish next to make your own simple example to me with all detailed pls
#93 Help Me ! » percentage growth vs actual growth meaning » 2021-12-06 05:10:28
- Hannibal lecter
- Replies: 6
Hydroelectric power is electric power generated by the
force of moving water. Figure 1.15 shows6 the annual
percent growth in hydroelectric power consumption by
the US industrial sector between 2004 and 2009.
(a) Find the largest time interval over which the percentage growth in the US consumption of hydroelectric
power was a decreasing function of time. Interpret
what decreasing means, practically speaking, in this
case.
(b) Find the largest time interval over which the actual
US consumption of hydroelectric power was a decreasing function of time. Interpret what decreasing
means, practically speaking, in this case.
I know (a) answer is the percentage growth was a decreasing function from (2005 to 2007)
but in (b) the book solution said actual US consumption interval was (2004–2007)
what is the difference before I see the book solution I thought it's also (2005 to 2007) same answer!
it's being two days I'm thinking about that and I didn't get the key
how it's 2004 to 2007???!!! the consumption is increased from 2004 to 2005 then decreased from 2005 to 2007
so we shouldn't include 2004
#94 Re: Help Me ! » percentage point » 2021-12-06 03:23:41
Let's have another example. The boss of a small company announces that the company is doing so well that everybody is going to get a 10% pay rise. The workers think great! They were getting $200 a week. Now they'll get $220. That's an extra $20 to spend (I'll ignore Uncle Sam for now)
Bob
the increase here is 10% as mention because 10% of 200 is 20 that's a percent increase right
but what is the percentage point here?
#95 Re: Help Me ! » annual sea level (function of time question) » 2021-12-05 18:34:27
yes I mean 1983, I knew there is a mistake but wanted to make sure
#96 Re: Help Me ! » percentage point » 2021-12-05 11:29:30
in Wikipedia it said :
percentage point or percent point is the unit for the arithmetic difference of two percentages. For example, moving up from 40 percent to 44 percent is an increase of 4 percentage points, but a 10-percent increase in the quantity being measured
I notice it said " but a 10-percent increase in the quantity being measured"
is there a simple example to explain that in real life time
#97 Help Me ! » percentage point » 2021-12-05 10:23:30
- Hannibal lecter
- Replies: 4
Hi, I find in math is fun site on this link talking about percentage point :
https://www.mathsisfun.com/percentage-points.html
in start the site said :
Example: Your earnings per sale went from 4% to 5%
That is a rise of 1 Percentage Point
(But is a 25% rise in your earnings!)
but I didn't find an live example may you make to me an example
like I'm selling a laptop by 100$ or any small little example explain how I'll be earn rising 25%!
#98 Help Me ! » annual sea level (function of time question) » 2021-12-05 03:24:21
- Hannibal lecter
- Replies: 2
Table 1.4 shows the average annual sea level, S, in meters, in Aberdeen, Scotland,8 as a function of time, t,
measured in years before 2008
Q) In what year was the average sea level 7.019 meters?
6.957 meters?
I found in book solution this answer : Looking at the table, we see that the average annual sea level was 7.019 fifty years before 2008, or in the year 1958.
and the average sea level was 6.957 meters 125 years before 2008, or in 1883
but how is that I see on table is 25! and 2008-25 is = 1993
the solution is it's fifty years before 2008!
is there a mistake right?
#99 Re: Help Me ! » my last question this month I know I made you tired from me » 2021-12-05 03:18:51
every answers of you is very helpful thank you so much I'm just being reading carefully and in accurate way and slowly and understand it
all of your answers helped me since I'm in the forums but I just don't say "thanks" in a comments because I think you prefer to talk about the subject only no side talk only discussions on the topic that the user posted so I just say thanks inside my mind I said thank you without reply on comments if I didn't understand your answer I'll 100% tell you that in the comment I promise I'm honest
#100 Help Me ! » my last question this month I know I made you tired from me » 2021-12-04 14:09:31
- Hannibal lecter
- Replies: 2
I'll provide answers for this question I have the answer but I have a question about the last section
please this question is very necessary for me and it's very silly in the same way
Residents of the town of Maple Grove who are connected
to the municipal water supply are billed a fixed amount
monthly plus a charge for each cubic foot of water used.
A household using 1000 cubic feet was billed $40, while
one using 1600 cubic feet was billed $55.
(a) What is the charge per cubic foot? answer : = $0.025/cu. ft
(b) Write an equation for the total cost of a resident’s Answer : c = b + 0.025w, b = 15, thus : c = 15 + 0.025w,
water as a function of cubic feet of water used.
(c) How many cubic feet of water used would lead to a
bill of $100? Answer of b section is : We need to solve the equation 100 = 15 + 0.025w, which yields w = 3400. It costs $100 to use 3400 cubic feet of
water
the manual solution of section b is confusing me.. I mean I can solve 100 question like that but without understanding it mentally
how to understand this mentally?
he put $100 = $15 + 0.025w
the solution of section a and section b is very easy and I know them
but the last section (b) is confusing me, in which law he put 100 dollar on the left and the other quantity (15 + 0.025w) to find how many cubic feet of water leads to 100$
what is that called in algebra, if you refer me to a link I will open it but I will not understand I need your own answer please if anyone know to to tell me that in easy way
I mean it's interactive math and interactive question, I need interactive answer too not just put 100 and solve the equation and find the cost, I can solve a lot of this question in future but someday I'll forget how to solve it! because I don't have the concepts in my mind and I don't understand this mentally