1. Writing Algebraic Expressions to Solve Word Problems.
How many minutes in 1 hour,
14 hours, in "n" hours?

2. Algebra is used every day to solve everyday problems.
For example:
You have a job and you get paid $8.25 an hour.
You want to figure out how much pay you will receive if you worked 16 hours.

3. You can write in words, I get paid $8.25 for every hour I work.
Algebraically, you would write:
$8.25h
which means 8.25 TIMES the number of hours you worked.

4. You should always write the formula FIRST for every question
SO, you would write
$8.25h = pay
Then, substitute the number of hours into the formula.
$8.25(16) = p (pay)
Calculate the result
Your pay would be $132.00
Write your answer as p = $132.00

5. Now it’s your turn.
Using the formula, calculate your pay if you worked:
20 hours?
32 hours?
18.5 hours?
22 hours?
110 hours?
Every question must start with the formula
$8.25h = p
Then substitute into the formula the hours that you worked.
Remember the answer is MONEY and should be in that form!

6. Now the same question with a twist!
If you got paid $189.75, how many hours did you work?
You get paid $8.25 an hour.
You can divide the pay by your rate of pay, ($8.25) to get the number of hours you worked.
Algebraically, it would look like this.
Calculate and you find:
You worked, 23 hours!

7. New Problems Some problems require that you know basic facts.
How many seconds in a minute?
How many minutes in an hour?
How many hours in a day?
How many days in a week?
How many days in a year?
How many weeks in a year?
How many months in a year?
How many centimetres in a metre?
How many metres in a kilometre?

8. How Many Days in Three Weeks?
Since you know that there are 7 days in a week, you can write:
7 days X the number of weeks = the number of days in a week.
Or Algebraically:
7(w) = d
Substitute into the formula what you know.
7(3)= d Calculate d = 21
There are 21 days in three weeks!

9. How many hours in four days?
There are 24 hours in one day. So
24d = hours in day
24 (4) = h
h = 96
There are 96 hours in 4 days.

10. Homework
You KNEW it was coming! 

11. Using the facts, write a formula for each and solve.
How many days in 3 weeks?
How many hours in 4 days?
How many cm in 1500 metres?
How many months in 13 years?
How many weeks in 7 years?
How many years in 3250 weeks? (careful)
How many years in 250 months? (careful)
How many minutes in 4 hours?
How many hours in 17 days?
How many kilometres in 4509 metres? (careful)

12. This Slide Show can be found at February Homework on our Math Web Site at: