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In the previous lesson you learned how to
translate a verbal expression to an algebraic expression. This
lesson will give you more examples and practice changing parts of word
problems into algebraic expressions.
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Quick Review: |
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15 less than a
number |
n - 15 |
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a number plus 18 |
n + 18 or
18 + n |
Now let's explore how this
can be used in setting up word problems.
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When translating, you must begin with a "let" statement.
In a "let" statement you "let" a variable stand for the one
quantity that you are starting with. You will then "build"
on that variable to express the other unknown. |
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Example #1:
Joe is 10 years older than Henry. Give an expression
for Joe's age. |
| Step one:
Write your "Let" statement |
In this case, let n
= Henry's age (You are starting with Henry's age and looking for Joe's age) |
| Step two: Think how
you will use the "10" |
10 years older means
"plus 10" |
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Henry's age = n
Joe's age = n + 10 |
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Example #2:
Molly is 4 years younger than Jill. Give an expression
for Molly's age. |
| Step one:
Write your "Let" statement |
In this case, let n
= Jill's age (You are starting with Jill's age and looking for Molly's age) |
| Step two: Think how
you will use the "4" |
4 years younger
means "minus 4" |
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Jill's age = n
Molly's age = n -4 |
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Example #3: Gas costs $2 more
this year then it did last year. Give an expression for the cost
of gas this year. |
| Step one:
Write your "Let" statement |
In this case, let n
=cost of gas last year (you are starting with last year's price
and looking for this year's price) |
| Step two: Think how
you will use the "2" |
$2 more means "plus
2" |
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n = cost of gas this year
n + 2 = cost of gas this year |
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Example #4: Ellen babysat for two
nights. On the second night, she earned 2 times the amount
she earned the first night. Give an expression for the
amount she earned the second night, if n = the amount she earned
the first night. |
| Step one:
Write your "Let" statement |
In this case, let n
=amount earned the first night (you are starting with first
night's earnings and looking for second night's earnings) |
| Step two: Think how
you will use the "2" |
2 times means
multiply by 2 |
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n = money earned on first
night |
2n = money earned second night |
Let's Practice
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