Writing Expressions and Equations

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Writing Expressions and Equations

• 7.1

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Objective

• Today you will learn how to write variable
  expressions and equations.
• Word Watch
• -verbal model

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In the Real World

• You are exploring a cave in which rock formations
  called stalagmites grow up from the cave floor.
  The tour guide informs you that the tallest
  stalagmite in the cave is in a pool of water 55
  feet deep, and the distance between the tip of
  the stalagmite and the surface of the water is 41
  feet. How tall is the stalagmite?

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Translating Phrases and Sentences

• To solve real-world problems, you need to
  translate verbal phrases and sentences into
  variable expressions and equations.
• Can you think of any key words that indicate
  addition, subtraction, multiplication, and
  division?

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(No Transcript)
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Translating Verbal Phrases

• Verbal Phrase expression
• a. A number increased by 5 x 5
• b. 7 less than a number x 7
• c. 3 more than twice a number 2x 3
• d. 4 decreased by the quotient of a number and 7
  4 -

x 7
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Translating Verbal Sentences

• Verbal sentence equation
• a. 16 increased by a is 27 16 y 27
• b. the difference of twice the and 3 equals
  -4 2y-3-4
• c. the product of and a is 36 y
  36
• d. -3 is equal to twice the sum of a number and 2
  -32(y2)

1 2
1 2
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? YOUR TURN!! ?

• Write the verbal phrase or sentence as a variable
  expression or equation. Let n represent the
  number.
• 1. 14 added to a number
• 2. of a number decreased by 22
• 3. 42 divided by a number equals 7
• 4. 5 minus twice a number is 17

n 14
1 2
1 2
n - 22
42 n
7
5 2n 17
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• You can use verbal models to solve real-world
  problems. A verbal model uses words to describe
  ideas and math symbols to relate the words

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Writing and Solving an Equation

• To find the height of the stalagmite described at
  the beginning of the lesson, you can write and
  solve an equation. First write a verbal model.

Distance between tip of stalagmite and water
surface
Height of stalagmite
Depth of water



41
55
h

The height of the stalagmite is 96 feet.
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? YOUR TURN!! ?

• Use mental math to solve the following equation.
• While hiking you descend 2,000 feet from the
  start of a trail to an elevation of 5,200 feet.
  Write and solve an equation to find the elevation
  at the start of the trail.

n 2,000 5,200 n 7,200 ft
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THOUGHT OF THE DAY!

• TYPEWRITER is the longest word that can be made
  using the letters only on one row of the
  keyboard.