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September 29, 2009
Math 102
Objective: Students will learn how to add integers.
Aim: How do number lines help us to add
integers?
NYS Mathematics Standards: 7.N.12
Prior Knowledge: Find each sum:
5 + 7 = ____
25 + 0 = ____
11 + 21 = ____
12 + 86 = ____
Mini-lesson:
To add positive numbers on a number line, begin at the
first number. Move right the same number of spaces as the
second number.
To add negative numbers on a number line, begin at the
first number. Move left the same number of spaces as the
second number.
Ex.
-2
+ (-3)
Start here, then move
LEFT 3 units…
Guided Practice:
Find the sum of -1 and 3. Use a number line.
1. Graph the first number.
2. Start at -1
3. Since 3 is a positive integer, move right 3
units.
Start here, then move to the RIGHT 3 units…
Write the Sum. -1 + 3 = 2
Independent Practice:
Complete Exercises 23, 26, 30, 34, 35
Mr. Brooks will visit each desk, review your work, and answer
any questions you may have.
Group Activity (Lesson Extension):
(Mr. Brooks will hand out red and yellow counters)
Find the sum of 2 and -6. Use counters.
1. Write the addition expression 2 + (-6).
2. Use 2 positive (yellow) counters to represent the first
number.
3. Use 6 negative (red) counters to represent the second
number.
4. You can make 2 zero pairs (1 red and 1 yellow cancel
each other out).
5. There are 4 negative counters left.
6. Write the difference. 2 + (-6) = -4
Assessment: Which are correct? If not, why not?
1. -8 + 3 = -11 ___________
2. The number line shows -2 + 5 = 3 _______
3. The sum of -6 and -9 is -15 ________
Homework:
8-1 Skills Practice worksheet