Mrs. bell has a rain gauge outside. on a very rainy day, the gauge measured 2.5 inches. the actual amount of rain that fell was 2.3 inches. to the nearest tenth, what is the percent error in mrs. bell's measurement?

The measurement error is defined as the difference between the measured value and the "true value".
 We have then that the error is given by:
 E = 2.5-2.3
 E = 0.2 inches
 The error percentage is:
 % E = (0.2 / 2.3) * 100 = 8.7%
 
 The percent error in Mrs. Bell's measurement is:
 % E = 8.7%