Final answer:
The measurement of a fish at 10.5 inches contains three significant figures, as the '10' is certain and the '.5' is the estimated part that also counts as a significant figure.
Step-by-step explanation:
The measurement of 10.5 inches involves a consideration of significant figures. Significant figures are the digits in a measurement that are known with a degree of certainty, plus one digit that is estimated. In the case of the measurement of the fish at 10.5 inches, there are three significant digits. The digits '10' represent the certain part of the measurement, while the '.5' represents the tenths place and is the estimated part of the measurement but still counts as a significant figure.
In general, significant figures reflect the precision of the measuring tool used. The usage of significant figures helps to ensure that figures reported in scientific and technical contexts accurately reflect the precision of the measurements taken. For example, a ruler that provides measurements to the nearest tenth of an inch enables the user to estimate to the nearest hundredth. Therefore, in the measurement 10.5 inches, '10' and '5' are all significant, and we would say that the number has three significant figures.