A calculator answer of 423.6059 must be rounded off to three significant figures. What answer is reported
The answer reported would be 424.
To round off the calculator answer of 423.6059 to three significant figures, you need to identify the first three most significant digits. In this case, they are "4", "2", and "4". The digit immediately after the third significant digit is "3".
As the digit "3" is less than 5, you do not need to round up. Therefore, the rounded answer to three significant figures is 424.