1. Using inspection, mental math
Eg. a + 4 = 12
8 + 4 = 12
12 = 12
Eg. a + 4 = 12
8 + 4 = 12
12 = 12
Ask yourself what something + 4 = 12 or 12 - something = 4
Try these:
14 = k + 5
14 = 9 + 5
t - 3 = 11
14 - 3 = 11
10 - y = 8
10 - 2 = 8
2. Model (make a picture) and solve
Eg.
Bill rides 4 km to the bridge then rides to work. In total he rides 11 km. How far from the bridge to work?
4 + y = 11
4 + 7 = 11
3. Apply the opposite operation
Eg. c + 22 = 56
- 22 = -22
c = 34
Check- c + 22= 56
34 + 22 = 56
56 = 56
1st step - Isolate the variable (get the letter by itself)
2nd step - Apply the opposite operation
3rd step - Check your answer. Substitute the answer for the letter of the original equation
Opposite operation - An operation that "undoes" another operation
* subtraction and addition are opposites
* division and multiplication are opposites
Solve by applying the opposite operating - Check your answer:
1. n + 7 = 26
- 7 = -7
n = 19
Check - n + 7 = 26
19 +7 = 26
26 = 26
2. d - 3 = -5
+3 = +3
d = -2
Check - d - 3 = -5(-2) - 3 = -5
-5 = -5
Page 398-401 # 1-22 is HOMEWORK!
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