Question 39 UFIV02 - Assistant Engineer - UFIV

The Correct Answer is D ### Explanation of Why Option D (97.57 mg/L) is Correct The question requires converting a measurement of water hardness from grains per gallon (gpg) to milligrams per liter (mg/L). The standard conversion factor for water hardness (assuming the hardness is expressed as Calcium Carbonate, CaCO3) is approximately: $$1 \text{ grain per gallon (gpg)} \approx 17.118 \text{ milligrams per liter (mg/L)}$$ To find the total hardness in mg/L, multiply the given hardness in gpg by the conversion factor: $$\text{Hardness (mg/L)} = \text{Hardness (gpg)} \times \text{Conversion Factor}$$ $$\text{Hardness (mg/L)} = 5.7 \text{ gpg} \times 17.118 \frac{\text{mg/L}}{\text{gpg}}$$ $$\text{Hardness (mg/L)} = 97.5726 \text{ mg/L}$$ Rounding to the precision offered by the option yields **97.57 mg/L**. --- ### Explanation of Why Other Options are Incorrect * **A) 0.333 mg/L:** This result is far too small. It appears to be the result of inverting the conversion (5.7 divided by 17.1) and using the wrong operation, or a severe decimal error. * **B) 0.9748 mg/L:** This value is incorrect by a factor of approximately 100. This could result from an error in decimal placement or an application of the wrong metric conversion factor. * **C) 9.757 mg/L:** This result is incorrect by a factor of 10. This is a common distractor error resulting from shifting the decimal point one place to the left during calculation, when the correct answer is 97.57 mg/L.