A student is using a graduated cylinder to measure the volume of water and reports a reading of 18 mL. The teacher reports the value as 18.4 mL. What is the...

The student's percent error can be calculated by using the formula:
Percent Error = |(Measured Value - True Value) / True Value| * 100%
In this case, the measured value is 18 mL, and the true value reported by the teacher is 18.4 mL.
Let's substitute the values into the formula:
|(18 mL - 18.4 mL) / 18.4 mL| * 100%
Simplifying the formula:
|(-0.4 mL) / 18.4 mL| * 100%
Taking the absolute value of the fraction:
|-0.0217| * 100%
Calculating the absolute value:
0.0217 * 100%
Multiplying by 100%:
2.17%
Therefore, the student's percent error is 2.17%.
Note: It is important to note that in this case, the student's measurement was lower than the true value, causing a negative difference. By taking the absolute value of the fraction in the formula, we ignore the negative sign and only consider the magnitude of the error.