We have to round off each measurement to the number of significant figures.
The correct answers are: 265.9, 0.00045 and 65 respectively.
265.991 when expressed in 4 significant figure it rounds off as 265.9 because 265.9 represents the value 265.991.
0.0004513 when expressed in 2 significant figure it rounds off as 0.00045 because zero before and after decimal are not significant.
6593 when expressed in 2 significant figure it rounds off as 65.
