11.8 Compound interest and half life.notebook November 08, 2017
Compound Interest AND Half Lives
Nov 21:43 PM
What is compound interest??
This is when a bank pays interest on both the principal amount AND on accrued interest.
**This is different from simple interest....how is that? • Simple interest is interest earned solely on the principal amount. • Remember I=prt??
Nov 21:43 PM 1 11.8 Compound interest and half life.notebook November 08, 2017
Let's take a look at a chart when interest is compound at an annual rate of 8%
Interest Rate Time Periods in a Earned Per Compounded Year Period annually 1 8% per year 8% / 2 periods so..... semiannually 2 4% every 6 months 8% / 4 periods so...... quarterly 4 2% every 3 months 8% / 12 periods so..... monthly 12 0.6% every month
Nov 21:47 PM
How do we find compound interest?
Nov 21:53 PM 2 11.8 Compound interest and half life.notebook November 08, 2017
$1,500 at 7% compounded annually for 3 years
Nov 22:08 PM
Suppose your parents deposited $1500 in an account paying 6.5% interest compounded quarterly when you were born. Find the account balance after 18 years.
Nov 38:29 AM 3 11.8 Compound interest and half life.notebook November 08, 2017
You deposit $200 into a savings account earning 5% compounded semiannually. How much will it be worth after 1 year? After 2 years? After 5 years?
Nov 38:29 AM
What is a halflife?
A halflife is the length of time it takes for one half of the substance to decay into another substance.
Nov 22:09 PM 4 11.8 Compound interest and half life.notebook November 08, 2017
We will use the exponential function model to determine half lives:
a = your initial amount (what you start with) b = always 0.5 or 1/2 to represent the half life (REMEMBER b is always the growth or decay factor in this case DECAY) x = the number of times your half life occurs
Nov 22:10 PM
The halflife of iodine124 is 4 days. A technician measures a 40mCi sample of iodine124. a. How many halflives occur in 16 days?
b. How much iodine124 is left in the sample after 16 days?
Nov 38:30 AM 5 11.8 Compound interest and half life.notebook November 08, 2017
The halflife of carbon11 is 20 minutes. A sample of carbon11 has 25 mCi. a. How many halflives occur in 1 hour?
b. How much carbon11 is left in the sample after 1 hour?
Nov 38:34 AM
A patient is given 30 grams of iodine131. A halflife for this substance is 8 days. How much of the substance remains in their system a. after 8 days?
b. after 16 days?
Nov 22:14 PM 6