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Solve an Equation that Contains Decimals
Solve 3.5x 37.9 0.2x. Round to the nearest tenth.
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INT
2
EXAMPLE
Student Help
Solution
3.5x 37.9 0.2x
Write original equation.
3.3x 37.9 0
Subtract 0.2x from each side.
ANSWER CHECK
3.3x 37.9
Add 37.9 to each side.
3.3x
37.9
3.3
3.3
Divide each side by 3.3.
x 艐 11.48484848
Use a calculator to get an
approximate solution.
x 艐 11.5
Round to nearest tenth.
The solution is approximately 11.5.
✓
3.5x 37.9 0.2x
3.5(11.5) 37.9 ⱨ 0.2(11.5)
2.35 艐 2.3 ✓
Write original equation.
Substitute 11.5 for each x.
Rounded answer is reasonable.
Solve an Equation that Contains Decimals
Solve the equation. Round to the nearest tenth.
4. 2.4x 0.9 12.4
5. 1.13y 25.34 0.26y
6. 14.7 2.3x 4.06
7. 3.25n 4.71 0.52n
ROUNDING ERROR Using a rounded solution in a real-life situation can lead to
a rounding error, as in Example 3.
EXAMPLE
3
Round for a Practical Answer
Three people want to share equally in the cost of a pizza. The pizza costs
$12.89. What is each person’s share?
Solution
Find each person’s share by solving 3x 12.89.
3x 12.89
Write original equation.
x 4.29666. . .
Use a calculator to divide each side by 3.
Exact answer is a repeating decimal.
x ⬇ 4.30
Round to nearest cent.
ANSWER Each person’s share is $4.30.
Three times the rounded answer is one cent too much due to rounding error.
164
Chapter 3
Solving Linear Equations
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