1. 7.2 Applications of Linear Equations
Part 2: Other Word Problems

2. Simple Interest
The formula for simple interest is I = prt, where p is the “principle”, r is the “rate” (converted to a decimal), and t is “time” (in years).
Previously, we were calculating interest for a one year period. Since t = 1, we just used I = pr.

3. Calculating Simple Interest
Elizabeth receives an inheritance. She plans to invest part of it at 9% and $2000 more than this amount in a less secure investment at 10%. To earn $1150 per year in interest, how much should she invest at each rate?
Amount
Invested ($)
Rate of
Interest
Interest for
One Year

4.  Dezneil earned $12,000 last year by giving tennis lessons
 Dezneil earned $12,000 last year by giving tennis lessons. He invested part at 3% simple interest and the rest at 4%. He earned a total of $440 in interest. How much did he invest at each rate?
Amount
Invested ($)
Rate of
Interest
Interest for
One Year

5. Monetary Denomination Problems
Problems that involve different denominations of money or item with different monetary values are very similar to mixture and interest problems.
Money Problems
Number x Value of one = Total value

6. Solving a Monetary Denomination Problem
A bank teller has 25 more five-dollar bills than ten-dollar bills. The total value of the money is $200. How many of each denomination of bill does he have?
Number
of Bills
Denomination
Total Value

7.  Amber found some coins under her sofa pillows
 Amber found some coins under her sofa pillows. There were equal numbers of nickels and quarters, and twice as many half-dollars as quarters. If she found $2.60 in all, how many of each denomination of coin did she find?
Number
of Coins
Denomination
Total Value

8. Distance, Rate, Time Relationship
The relationship between distance, rate, and time can be given in the following formulas:

9.  Solve each of the following.
The speed of sound is 1088 feet per second at sea level at 32˚F. How far does sound travel in 5 seconds under these conditions?
The winner of the first Indianapolis 500 race drove at an average speed of mph. How long did it take him to complete the 500 mile race?
In the 2000 Olympic Games, Dutch swimmer Inge de Bruijn won the women’s 50-m freestyle swimming event in seconds. What was her rate?

10. Using a Table
Jeff can bike to work in ¾ hour. By bus, the trip takes ¼ hour. If the bus travels 20 mph faster than Jeff rides his bike, how far is it to his workplace?
Rate x Time = Distance
Bike
Bus

11.  Two steamers leave a port on a river at the same time, traveling in opposite directions. Each is traveling 22 mph. How long will it take for them to be 110 miles apart?
Rate x Time = Distance
First Steamer
Second Steamer