3.9 Problem Solving: Writing an Equation

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3.9 Problem Solving Writing an Equation
1. Read the problem and list your variables.
2. Write and solve an equation.
3. Check your answer to see if it makes sense!!!
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The sum of three consecutive integers is 105 find
the three integers.
x 1st integer
x 1 2nd integer
x 2 3rd integer
x x 1 x 2 105
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x x 1 x 2 105
3x 3 105
-3 -3
3x 102
x 34
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The sum of three consecutive integers is 105 find
the three integers.
x 1st integer
x 1 2nd integer
x 2 3rd integer
34, 35, 36
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Usually, the second item listed is going to be
your variable.
You have to list it and then use that variable to
write the other quantity.
You can only use one variable to write the
equation.
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A marathon had 448 more local runners than
visiting runners. The total number in the race
was 3640. Find the number of local runners and
visiting runners
v visiting runners
v 448 local runners
v v 448 3640
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v v 448 3640
2v 448 3640
- 448 -448
2v 3192
v 1596
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A marathon had 448 more local runners than
visiting runners. The total number in the race
was 3640. Find the number of local runners and
visiting runners
v visiting runners
1596
v 448 local runners
2044
9
A doberman weighs twice as much as a cocker
spaniel. If together the dogs weigh 135 pounds,
how much does each dog weigh?
s cocker spaniel
2s doberman
s 2s 135
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s 2s 135
3s 135
s 45
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A doberman weighs twice as much as a cocker
spaniel. If together the dogs weigh 135 pounds,
how much does each dog weigh?
s cocker spaniel
45
2s doberman
90
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Homework

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