A dialysis unit requires 78.5 L of water. What is the estimated digit?

The estimated digit is 5

Explanation:

Significant figures are the digits of a number that carry meaning and contribute to the precision of the given number or measurement.

Whereas, the estimated digit in a number is the last significant figure of the given number or measurement

Therefore, the given measurement

78.5 L: has three significant figures, because the non-zero digits are considered significant figures.

The estimated digit is 5, as it is the last significant figure of the measurement.