Solving Addition Equations

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Solving Addition Equations
Warm Up
Problem of the Day
Lesson Presentation
Course 1
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Warm Up Determine whether each value is a
solution. 1. 86 x 102 for x 16 2. 18 x
26 for x 4 3. x 46 214 for x 168 4. 9 x
35 for x 26
yes
no
yes
yes
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Solving Subtraction Equations
Problem of the Day After Renee used 40 m of
string for her kite and gave 5 m to her sister
for her wagon, she had 8 m of string left. How
much string did she have to start with?
53 m
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Learn to solve whole-number addition equations.
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The equation h 14 82 can be represented as a
balanced scale.
To find the value of h, you need h by itself on
one side of the scale.
To get h by itself, first take away 14 from the
left side of the scale. Now the scale is
unbalanced.
To rebalance the scale, take away 14 from the
other side.
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Taking away 14 from both sides of the scale is
the same as subtracting 14 from both sides of the
equation.
h 14 82
14
14
h 68
Subtraction is the inverse, or opposite, of
addition. If an equation contains addition, solve
it by subtracting from both sides to undo the
addition.
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Additional Example 1A Solving Addition Equations
Solve the equation. Check your answer.
x 87 152
x 87 152
87 is added to x.
87
87
Subtract 87 from both sides to undo the addition.
x 65
Check x 87 152
Substitute 65 for x in the equation.
?
65 is the solution.
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Additional Example 1B Solving Addition Equations
Solve the equation. Check your answer.
72 18 y
72 18 y
18 is added to y.
18
18
Subtract 18 from both sides to undo the addition.
54 y
Check 72 18 y
Substitute 54 for y in the equation.
?
54 is the solution.
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Try This Example 1A
Solve the equation. Check your answer.
u 43 78
u 43 78
43 is added to u.
43
43
Subtract 43 from both sides to undo the addition.
u 35
Check u 43 78
Substitute 35 for u in the equation.
?
35 is the solution.
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Try This Example 1B
Solve the equation. Check your answer.
68 24 g
68 24 g
24 is added to g.
24
24
Subtract 24 from both sides to undo the addition.
44 g
Check 68 24 g
Substitute 44 for g in the equation.
?
44 is the solution.
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Additional Example 2 Social Studies Application
Johnstown, Cooperstown, and Springfield are
located in that order in a straight line along a
highway. It is 12 miles from Johnstown to
Cooperstown and 95 miles from Johnstown to
Springfield. How far is it from Cooperstown to
Springfield?
distance between Johnstown and Springfield
distance between Johnstown and Cooperstown
distance between Cooperstown and Springfield


95 12
d
95 12 d
12 is added to d.
12
12
Subtract 12 from both sides to undo the addition.
83 d
It is 83 miles from Cooperstown to Springfield.
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Try This Example 2
Patterson, Jacobsville, and East Valley are
located in that order in a straight line along a
highway. It is 17 miles from Patterson to
Jacobsville and 35 miles from Patterson to East
Valley. How far is it from Jacobsville to East
Valley?
distance between Patterson and East Valley
distance between Patterson and Jacobsville
distance between Jacobsville and East Valley


35 17
d
35 17 d
17 is added to d.
17
17
Subtract 17 from both sides to undo the addition.
18 d
The distance between Jacobsville and East Valley
is 18 miles.
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Lesson Quiz
Solve each equation. 1. x 15 72 2. 81 x
24 3. x 22 67 4. 93 x 14
x 57
x 57
x 45
x 79
5. Kaitlin is 2 inches taller than Reba. Reba is
54 inches tall. How tall is Kaitlin?
56 inches