Transcript solving word problems

SOLVING WORD
PROBLEMS
LESSON 3
Think, Plan and Do, Look Back
► When
solving word problems this approach will
help you through the process of gathering
information to solve word problems.
► THINK
- What information is important?
► PLAN - Identify the unknowns with a variable
► DO - Make an equation by translating.
► LOOK BACK - Check your answer in the original
problem. Are all the conditions satisfied? Can the
problem to solved differently?
Steps to Solving Word
Problems
1.
2.
3.
4.
5.
Use a variable to represent the unknown
quantity
Express any other unknown quantities in
terms of this variable, if possible.
Write an equation, and solve it.
State the answer to the problem.
Check your answer by substituting in the
problem.
The sum of two numbers is 48. One
number is three times as great as the
other. Find the two numbers.
Let the
1st
number be represent by x
Let the 2nd number be represent by 3x
Equation: x + 3x = 48
x + 3x = 48
4x = 48
4x = 48
4
4
x = 12
Check:
x + 3x = 48
(12) + 3(12) = 48
12 + 36 = 48
48 = 48
Things to Remember:
Use a variable to represent
the unknown quantity
Express any other unknown
quantities in terms of
this variable, if
possible.
Write an equation, and
solve it.
State the answer to the
problem.
Check your answer by
substituting in the
The sum of three consecutive
numbers is 114. Find the numbers.
Let x represent the 1st number.
Let (x + 1) represent the 2nd number.
Let (x + 2) represent the 3rd number.
Equation: x + (x + 1) + (x + 2) = 114
x + (x + 1) + (x + 2) = 114
Things to Remember:
Use a variable to represent the
unknown quantity
Express any other unknown
quantities in terms of this
variable, if possible.
Write an equation, and solve it.
3x + 3 = 114
State the answer to the
problem.
3x + 3 - 3 = 114 - 3
3x = 111
x = 37
3x = 111
3
3
x + 1 = 38
x + 2 = 39
Check your answer by
substituting in the
problem.
A number is doubled and then
decreased by 8. The result is 42.
Find the number
Let x represent the number.
Things to Remember:
Equation: 2x - 8 = 42
Use a variable to represent the
unknown quantity
2x - 8 + 8 = 42 + 8
Express any other unknown
quantities in terms of this
variable, if possible.
2x = 50
Write an equation, and solve it.
2x = 50
2
2
Check:
x = 25
2(25) - 8 = 42
2x - 8 = 42
50 - 8 = 42
42 = 42
State the answer to the
problem.
Check your answer by
substituting in the
problem.
The sum of two consecutive even
numbers is 110. Find the numbers
Let x represent the 1st number.
Let (x + 2) represent the 2nd number.
Equation: x + (x + 2) = 110
x + (x + 2 ) = 110
2x + 2 - 2 = 110 - 2
x + 2 = 56
Use a variable to represent the
unknown quantity
Express any other unknown
quantities in terms of this
variable, if possible.
2x + 2 = 110
2x = 108
2x
108
=
2
2
x = 54
Things to Remember:
Check:
x + (x + 2) = 110
Write an equation, and solve it.
State the answer to the
problem.
(54) + (56) = 110
110 = 110
Check your answer by
substituting in the
problem.
Class work
► Check
solutions to Lesson 2(3) - Page 147 # 13, 14
► Copy down notes and examples
► Do Lesson 3 Worksheet