What is Interest: Definition and 296 Discussions

Interest, in finance and economics, is payment from a borrower or deposit-taking financial institution to a lender or depositor of an amount above repayment of the principal sum (that is, the amount borrowed), at a particular rate. It is distinct from a fee which the borrower may pay the lender or some third party. It is also distinct from dividend which is paid by a company to its shareholders (owners) from its profit or reserve, but not at a particular rate decided beforehand, rather on a pro rata basis as a share in the reward gained by risk taking entrepreneurs when the revenue earned exceeds the total costs.For example, a customer would usually pay interest to borrow from a bank, so they pay the bank an amount which is more than the amount they borrowed; or a customer may earn interest on their savings, and so they may withdraw more than they originally deposited. In the case of savings, the customer is the lender, and the bank plays the role of the borrower.
Interest differs from profit, in that interest is received by a lender, whereas profit is received by the owner of an asset, investment or enterprise. (Interest may be part or the whole of the profit on an investment, but the two concepts are distinct from each other from an accounting perspective.)
The rate of interest is equal to the interest amount paid or received over a particular period divided by the principal sum borrowed or lent (usually expressed as a percentage).
Compound interest means that interest is earned on prior interest in addition to the principal. Due to compounding, the total amount of debt grows exponentially, and its mathematical study led to the discovery of the number e. In practice, interest is most often calculated on a daily, monthly, or yearly basis, and its impact is influenced greatly by its compounding rate.

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  1. M

    Calculating Present Value of a Growing Annuity with Monthly Payments

    [b]1. 5. A twenty year annuity has end of month payments. The first year the payments are each $100. In subsequent years each payment increases by $10 over what it was the previous year. Find the present value of the annuity if i = 4% is the effective annual interest rate. Thank you
  2. B

    What would i tell why you interest in physics in an interview

    Hey Hey guys i have an interview in undergraduate physics on tommorow.What would i tell if they ask why do you interest in physics?Actually because i need to learn about Genaral realativity,M theory,string theory and so on. So is this an intelligent answer?Will they think i am an insane...
  3. C

    Interest in astrology and physics

    im a high school student who just recently found out i have an interest in astrology and physics and such, I am looking for a good website or something that can help me learn a lot of what i want to know before i go into college. i know this dose not belong in here i just didnt know where to...
  4. A

    Calculating Compound Interest: January 2010 Cash Balance Analysis

    Homework Statement January 1, 2010, opening cash balance is $20590.17. January 31, 2010, closing cash balance is $20626.89. Interest rate is 2.1%. Interest paid is $36.72. (There are 31 days in January 2010). I=interest A=amount (ie. P+I) P=principal i=interest rate per...
  5. M

    Solve the Science Club Fundraiser Puzzle - Compound Interest

    At a school fundraiser, the science club made 58% of their money selling juice, 27% selling cookies,and 15% selling appels . The club made 87% selling juice .How much did the club make selling cookies? How much did they make selling appels? Please help me figure this out i am completely lost...
  6. J

    Why do we take the no. of years to compound the interest as power?

    Why do we take the "no. of years to compound the interest" as power? Suppose interest is given at 12% annually, compounded once a year. At the end of the year we will have (A = starting amount): A( 1 + 0.12 ) But if it is compounded twice a year, then at the end of the year we will have...
  7. S

    Letter of Interest for an REU program?

    Hi all, I am in the process of applying for a few REU programs for this upcoming summer. Right now i am facing difficulties compiling the letter of interest. So, i thought someone here, who has enough experience, might point me to the right direction in terms of what are some of the most...
  8. R

    A good book that is an indicator of your interest in physics

    So these last couple of weeks, turning into months, I've been pondering whether to start a whole new career in Physics, but am still unsure of whether it's only that I want to change something in my life or whether it's my actual interest in physics. I don't want to make a bad decision (again?)...
  9. L

    Derivative of compound interest

    Homework Statement f(x) = (1/x+1)^x, find f'(x) Homework Equations derivative of a^x = ln(a) a^x The Attempt at a Solution When I differentiate i get ln((1+x)/x)*((1+x)/x)^x... However, this solution does not match what I should be getting. Am i differentiating wrong at some point...
  10. C

    Interest compounded monthly problem

    Hi again! Bob's credit card balance is $2000. Credit company charges 24% interest compounded monthly. 1) Amortize monthly payments to pay off in 3 years I'm not sure how to write the equations on the board, but I get $78.47 2) If Bob only pays $25 monthly minimum, what will his debt...
  11. phoenixthoth

    How to find a grad program by area of interest (math)

    Apart from Google, is there a site that offers the ability to search for (math) grad schools by specific research interests?
  12. drizzle

    Have you ever lost interest in physics?

    Have you ever lost interest in physics?! I’m afraid I have:cry:. I mean I suppose to hand in my thesis last month, but after working as a TA and meeting lots of ‘nerds’ I just lost interest in physics, I know it’s stupid but I couldn’t overcome the feeling, and I don't know what causes it. it’s...
  13. M

    Aero Design: Explore Hobby Flight Projects

    Afternoon everyone, I am becoming more interested in aerospace engineering -for a hobby more than anything. I am a mechanical design engineer, but have neve really crossed over into the basics of helicopter and plane design. I have recently Just finished designing a combat robot, and...
  14. ╔(σ_σ)╝

    Discovering Graph Theory: Is it Worth Taking for Rigor and Interest?

    I am planing to take a course in Graph theory at my university, but i have no idea what it is. I want to take something that is ,to some extent, rigorous and interesting. This is the course summary provided by my school : Introduction to graph theory and its applications with an emphasis on...
  15. D

    Incoming RIT Freshman Interested in CS & Math - What Should I Do?

    I'm an incoming freshman at RIT, starting this fall. I was accepted into the CS program and had planned on double majoring in CS and Math. I've been extremely interested in CS for many years now and have great experience with web and systems programming, computer maintenance, networking and so...
  16. marcus

    What causes the research interest in cosmology?

    I just happened to notice a way to gauge the degree of research interest in cosmology---which I think has something to do with its importance in uncovering new physics. What this does is search Stanford's Spires HEP database for the overall most highly cited physics papers that have appeared...
  17. F

    What Is Compound Interest and How Does It Differ From Other Types?

    I know interest is compute by formula interest=(All money person get) - expense but I hear there say compound interest, what is it ? after all how many interest is there ? Thank you
  18. K

    Engineering Engineering Student with Interest in theoretical Physics

    Hello everyone, I am a junior in aerospace engineering student at Georgia Tech, and out of my boredom for the month that I have off I have begun to be interested in theoretical physics, I was wondering if there were some good books to read at my level. Of course with AE, there is a lot of...
  19. I

    Compound Interest / Annuities problem

    Suppose that you are negotiating your bonus with your boss. She offers you three options for your bonus: Option A: You get $5000 right now Option B: You get 8 monthly payments of $650 starting 1 month from now Option C: You get $5300, but you have to wait 8 months before you get it Using an...
  20. R

    Recursive Def/Compounding Interest question

    Homework Statement When Mr. Howe retires at age 65 he expects to have a retirement account worth about $400,000. One month after he retires, and every month thereafter, he intends to withdraw $4000 from the account. The balance will be invested at 9% annual interest compounded monthly. a) Let...
  21. D

    Financial, Multiple Compound Interest Problem

    I am currently attempting to solve the following problem for a calculator I am constructing in Java. Company 1 pays A% Interest every T days Company 2 pays B% Interest (>A%) every T days Company 1 has an initial investment of $X dollars Company 2 requires an inital fee of $Y dollars to...
  22. P

    Solving Interest Problems: Compound Interest & PERT

    Homework Statement This is not a problem in my calculus book.However, I am sure this involves calculus. This is also not a question from an economics class, it is just curiosity. My question is: If I have a debt that is continually compounded, and I continually pay off the debt at a constant...
  23. S

    If you have interest in quantum optics

    If you have interest in quantum optics,and you have aleady taken quantum mechanics course,try this . http://info.phys.unm.edu/~ideutsch/Classes/Phys566F08/index.htm#schedule
  24. R

    Invest a dollar at 6% interest compounded monthly

    Homework Statement If you invest a dollar at 6% interest compounded monthly, it amounts to (1.005)^n, where n=# of months. If you invest 10$ at the beginning of each month for 10 years (120 months), how much do you have at the end of the 10 years? Homework Equations sum of a geometric...
  25. K

    Fortran Fortran - compounding interest

    I'm trying to write a program for compounded interest, but am having trouble with the formattting. Any ideas? This is what I have: program interest_calculations !name, Assignment 5-25, to calculate interest implicit none real :: A !future value of the account real :: r !annual percentage...
  26. J

    Extra Que for Interest: Voltage and Wire Resistance

    Hi! I was looking at notes about voltage and resistance, and this question popped into my head. Homework Statement If a certain length of wire ie)40m with an unknown resistance has a voltage of say 24V (random number) when hooked up to a battery, how does the voltage change throughout the...
  27. S

    Any recommendation for started physics book (to generate interest)

    as a present for a grade 8 junior, something basic yet interesting enough to spark her interest. any suggestions thanks!
  28. S

    Some (6) poems I have written. I hope you find them of interest.

    Removed.
  29. Q

    Continuously compunded interest

    Homework Statement The island of Manhattan was sold for $24 in 1626. Suppose the money had been invested in an account which compounded interest continually. a) How much money would be in the account in the year 2005 if the yearly interest rate was: i: 5%? ii: 7% The Attempt at a...
  30. A

    Exploring a New Interest in Sciences and Maths

    Wassup fellas, I'll take this opportunity to ask the same old worn out question which every noob asks. I absolutely loved sciences and mathematics back when I was in high school till 10th grade. Not saying I was some kinda super genius or something though. :) Kinda lost way after that. But...
  31. N

    Inflation-complicated compound interest

    Hi gang, I need help with a formula if somebody with an enormous brain and generous heart has some spare time. I need to work out what 9% of $60,000 ($5400) invested annual at 7% (net of fees and taxes) would grow to in 30 years, with the $60,000 increasing by 3% inflation each year (so the...
  32. C

    Continuous Compound Interest with changing capital

    Is there any equation/formula for continuous compound interest to which money is added (or substracted from) periodically? Or can one be derived? Thanks i.e. monthly interest rate is 50% and we add 1$ every month (:bugeye:) Initially: 1$ 1st Month: 1.6 + 1 = 2.6$ 2nd month: 4.3 + 1...
  33. N

    Continuously compounded interest

    Homework Statement I must give medication to a patient continuously, but at the same time the kidneys eliminate the 2,5 per cent of the medication. I need to have 90micrograms of medication at the end of 4 hours. The initial medication amount is zero. Normally, the limit of the compound...
  34. A

    Solving Interest Problems | Alg 2 Help Needed for Marianne's Loan

    Homework Statement Marianne borrowed 10000. She borrows from a friend at 8%, twice that amount from her bank at 9% and the rest from her Insurance at 5%. She pays a total of 830 in interest for the first year. How much did she borrow from EACH SOURCE?! Homework Equations ?? The...
  35. Phrak

    Economics: Forcing Interest Rates Low

    ECONOMICS "Any legislation to force intestest rates lower will probable have to wait for a new president." This is a quote from the talking heads at ABC news (ABC World News). What would be the effects of national legislation forcing mortgage lenders, by law, to make loans at a lower rate?
  36. U

    How can I calculate my savings with varying deposits using the interest formula?

    Homework Statement Using the following savings formula, where d is a uniform deposit, i= (interest rate)/(# times compounded per year), n is the total times compounded. As I understand it, this formula will tell me how much I will have after depositing a certain amount of money per...
  37. A

    I wnt to understand which is my interest

    i can't understand about my own interest! i don't know which one to choose as my subject as both of them fascinate me and i like both the topic. Those topics are:1-particle physics, its the topic in which we can understand the very beginning of things; 2-astro physics, a topic in which we can...
  38. M

    Compond interest word problem

    Homework Statement If the total interest earned on an investment at 8.2% compounded semiannually for 8.5 years was $1,175.98, what was the original investment? Homework Equations A=P(1+i)^n The Attempt at a Solution
  39. H

    Calculating Value of Investment: $5,000 at 6.3% Interest

    a sum of $ 5 000 is invested at a compound interest rate of 6,3% per annum. the value of the investmen vill exceed $ 10 000 after n full years. (a) write an inewuality to represent this information. (b) calculate the minimum value of n. please help. english is my second langue and I am a...
  40. marcus

    Quantum Gravity: Tracking Public Interest & Acceptance

    Some people talk as if they think the social statistics of science don't matter, but it's hard for me to believe they really think that. Stats on public perceptions and interest in science, and also stats on research publication, citations, faculty hiring etc., must sometimes be important to...
  41. rootX

    PF interest from Google insights

    http://google.com/insights/search/#cat=&q=physics%20forum&geo=&date=&clp=&cmpt=q India seem to beat everyone else. I thought US would be at 1. 1. India 100 2. Canada 84 :biggrin: 3. Australia 71 4. United States 70 5. United Kingdom 66 6. Germany
  42. T

    Solving Continuous Interest Formulas: What Causes the Difference?

    I was reviewing continuous interest formulas when something stumped me. The accepted formula for continuous interest is A=Pert, and the proof of it is simple enough to understand. However, my math book solves the formula in a different way. It starts with the standard model for growth...
  43. 4

    Analysing an IS Curve Shift with Fixed Interest Rate

    This is an econ question, i am not sure if i should post it here. Assume that initially the IS curve is given by IS1: Y = 12-1.5T-30i+2G, and that the price level P is 1, and the LM curve is given by LM1: M= Y(1-i). Initially, the home interest rate equals the foreign interest rate of 10%...
  44. X

    Career Advice for BSc Physics Student Interested in Asteroids, Meteors, Comets

    My first post to this forum and its with some thing to do with the career. I will be a BSc Graduate this year with major in physics.(In India) I am very much interested in the physics of "Asteroids, meteors, comets". I want to know what should I be getting into to later be in a position to...
  45. wolram

    Diminishing Results in Cosmology: Public Interest Fading?

    I think string theory and quantum loop theory are the instigators in destroying public interest in cosmology, pop articles promised so much ,but nothing emerged, i also think that funding of cosmology projects will decline with diminishing results, it is no fault of the scientist, just bad luck...
  46. O

    Help with Compound Interest Homework Problem

    i have five problems on this on my econ test tomorrow. PLEASE HELP! I've looked in my book and can't find anything! thank you :) Homework Statement Calculate compound interest: principal: 65,000 rate: 5.25% time: 1.5 years it doesn't say how long it's going to be compounded...
  47. B

    Does your interest in learning cease at a certain age?

    For instance, when a person graduates from college , do you think they've learned all they need to know and so they just apply the skills they acquired in college to society? Or do you think people just stop feeding there mind after they had kids? Of course, you need to learn parental skills...
  48. M

    Why does 90 degrees equal arccot(300/1000)?

    Hey everyone, I have recently developed a strong interest in physics. To the point where I am changing my major from computer science to computational physics. Anyway, I am having a problem understanding a formula in a book I have on relativity. The problem is: 90\circ = arcsec(300/1000)...
  49. G01

    Statement of Interest (Writer's Block)

    AAAAAGGGGGHHH! The ONLY thing I wanted to get done this weekend, the ONLY thing, was to right a statement of interest for my REU applications. As of now, I have an open Word document with the words "Statement of Interest" on the top of the page! This has been the most unproductive weekend...
  50. N

    Belgian Student Interested in Quantum Mechanics

    Hi, Currently I'm still in high school (I turn 17 in februari), but soon I'll be going to college. I live in Belgium (the Flemish -- also known as the Dutch -- part) and we have about 4 universities. I have a very strong interest in mathematics, physics and chemistry, more specifically...
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