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Writing Algebraic Expressions to Solve Word Problems.

Writing Algebraic Expressions to Solve Word Problems. How many minutes in 1 hour, 14 hours, in "n" hours?. Algebra is used every day to solve everyday problems. For example: You have a job and you get paid $8.25 an hour.

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Writing Algebraic Expressions to Solve Word Problems.

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  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 8.25TIMES 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 asp = $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: • 7days X the number ofweeks =the number ofdays 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: https://hamptongrade8math.wikispaces.com/

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