Math Problem Statement

When measuring the dimensions of a rectangular field, an error was introduced in which one side was recorded as being 9% larger than its actual length, while the other side was documented as being 7% shorter than its true length. Determine the percentage of error in the calculated area that arises from these measurements.

Solution

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Problem:

When measuring the dimensions of a rectangular field, an error was introduced in which one side was recorded as being 9% larger than its actual length, while the other side was documented as being 7% shorter than its true length. Determine the percentage of error in the calculated area that arises from these measurements.

Options:

  • A. 1.7%
  • B. 1.4%
  • C. 1.8%
  • D. 2.3%

Solution:

  1. Let the true dimensions of the rectangle be LL and WW:

    • True area Atrue=LWA_{\text{true}} = L \cdot W.
  2. Dimensions after errors:

    • The length becomes Lmeasured=1.09LL_{\text{measured}} = 1.09L (9% larger).
    • The width becomes Wmeasured=0.93WW_{\text{measured}} = 0.93W (7% smaller).
  3. Measured area: Ameasured=LmeasuredWmeasured=(1.09L)(0.93W)=1.090.93LWA_{\text{measured}} = L_{\text{measured}} \cdot W_{\text{measured}} = (1.09L) \cdot (0.93W) = 1.09 \cdot 0.93 \cdot L \cdot W

    Simplify: Ameasured=1.0137LWA_{\text{measured}} = 1.0137 \cdot L \cdot W

  4. Error in area: Error=AmeasuredAtrueAtrue100%\text{Error} = \frac{A_{\text{measured}} - A_{\text{true}}}{A_{\text{true}}} \cdot 100\%

    Substitute: Error=1.0137LWLWLW100%=(1.01371)100%\text{Error} = \frac{1.0137 \cdot L \cdot W - L \cdot W}{L \cdot W} \cdot 100\% = (1.0137 - 1) \cdot 100\%

    Simplify: Error=0.0137100%=1.37%\text{Error} = 0.0137 \cdot 100\% = 1.37\%

  5. Closest option:

    • The percentage error is approximately 1.4%, which matches Option B.

Final Answer:

B. 1.4%

Would you like a further breakdown or clarification on any step?


Follow-up Questions:

  1. How does each measurement error affect the total area independently?
  2. Can this error compound differently for other shapes, like circles or triangles?
  3. What are real-world implications of such small percentage errors in large fields?
  4. How can one mitigate or correct such measurement errors practically?
  5. Could alternative percentage error definitions yield a different result?

Tip:

Always consider the multiplicative nature of errors in products like area, as errors in dimensions are not simply additive.

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Math Problem Analysis

Mathematical Concepts

Percentage Error
Area of a Rectangle
Error Propagation

Formulas

A_true = L * W
A_measured = 1.09 * L * 0.93 * W
Error = ((A_measured - A_true) / A_true) * 100%

Theorems

Multiplicative nature of errors in product-based calculations

Suitable Grade Level

Grades 9-11