Expert: Richard J. Raridon - 6/9/2009

Question
1. One hundred dollars is invested at 7.2% interest compounded annually. Determine how much the investment is worth after 1 year.

2. One hundred dollars is invested at 7.2% interest compounded annually. Determine how much the investment is worth after 10 years.

3. One thousand dollars is invested at 12% interest compounded monthly. Determine how much the investment is worth after 1 year.

4. One thousand dollars is invested at 12% interest compounded monthly. Determine how much the investment is worth after 3 years.  

5. The value of a new $3500 sailboat decreases 10% per year. Find its value after 1 year.  

6. The value of a new $3500 sailboat decreases 10% per year. Find its value after 10 years.  

7. A culture of yeast doubles in size every 20 minutes. The size of the culture is now N0. Find its size in 12 hours.  

8. The radioactive gas radon has a half-life of approximately 3.5 days. About how much of a 100 g sample will remain after one week?  

9. How long will it take you to triple your money if you invest it at a rate of 6% compound annually?  

10. Sugar is put in a large quantity of water and the mixture is stirred. After 2 minutes, 50% of the sugar has dissolved. How much longer will it take until 90% of the sugar has dissolved?  

11. Ten years ago Michael paid $250 for a rare 1823 stamp. Its current value is $1000. Find the average annual rate of growth.  

12. A tractor that 4 years ago cost $8000, is now worth only $3200. Find the average annual rate of depreciation.  

Answer
1. $107.20
2. $200.42
3. $1126.82
4. $1430.77
5. $3150
6. 0 if it's 10% of the original value.  $1220 if it's 10% of the previous value
7. 6.87x10^10(NO)
8. 25g
9. 18.85 years
10. 4.64 minutes
11. 14.87%
12. 10% per year of the original value