This document provides instruction on solving addition equations in 3 steps or less: 1) It introduces solving addition equations by subtracting the number being added from both sides of the equation to "undo" the addition. 2) It provides examples of solving addition equations and checking the solutions. 3) It gives a social studies application example of finding the distance between two points using addition equations.

1. 2-5 Addition Equations
2-5 Addition Equations
Warm Up
Problem of the Day
Lesson Presentation
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2. 2-5 Addition Equations
Warm Up
Determine whether each value is a solution.
1. 86 + x = 102 for x = 16 yes
2. 18 + x = 26 for x = 4 no
3. x + 46 = 214 for x = 168 yes
4. 9 + x = 35 for x = 26 yes
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3. 2-5 Addition 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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4. 2-5 Addition Equations
Learn to solve whole-number addition
equations.
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5. 2-5 Addition Equations
h + 14 82
The equation h + 14 = 82 can be
represented as a balanced scale.
h ?
To find the value of h, you need h
by itself on one side of the scale.
h + 14
82 To get h by itself, first take away
14 from the left side of the scale.
Now the scale is unbalanced.
h 68
To rebalance the scale, take away
14 from the other side.
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6. 2-5 Addition Equations
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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7. 2-5 Addition Equations
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
x = 65 to undo the addition.
Check x + 87 = 152 Substitute 65 for x in the
?
65 + 87 = 152 equation.
?
152 = 152  65 is the solution.
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8. 2-5 Addition Equations
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
54 = y to undo the addition.
Check 72 = 18 + y Substitute 54 for y in the
?
72 = 18 + 54 equation.
?
72 = 72  54 is the solution.
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9. 2-5 Addition Equations
Check It Out: 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
u = 35 to undo the addition.
Check u + 43 = 78 Substitute 35 for u in the
?
35 + 43 = 78 equation.
?
78 = 78  35 is the solution.
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10. 2-5 Addition Equations
Check It Out: 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
44 = g to undo the addition.
Check 68 = 24 + g Substitute 44 for g in the
?
68 = 24 + 44 equation.
?
68 = 68  44 is the solution.
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11. 2-5 Addition Equations
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. Find the distance
d between Cooperstown and Springfield.
distance between distance between distance between
Johnstown and = Johnstown and + Cooperstown and
Springfield Cooperstown 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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12. 2-5 Addition Equations
Check It Out: 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. Find the distance d between
Jacobsville and East Valley.
distance between distance between distance between
Patterson and East = Patterson and + Jacobsville and
Valley Jacobsville 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
It is 18 miles from Jacobsville to East Valley.
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13. 2-5 Addition Equations
Lesson Quiz
Solve each equation.
1. x + 15 = 72 x = 57
2. 81 = x + 24 x = 57
3. x + 22 = 67 x = 45
4. 93 = x + 14 x = 79
5. Kaitlin is 2 inches taller than Reba. Reba is 54
inches tall. How tall is Kaitlin?
56 inches
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