Simplify :
245.67-34.5+67.098
we have :
=245.67+67.098-34.5 ( collecting numbers with similar signs )
=312.768-34.5 ( adding 245.67 and 67.098 to get 312.768)
=278.268 ( subtracting 34.5 from 312.768 to get 278.268)
Therefore 245.67-34.5+67.098=278.268
Write the decimal numbers as the decimal fraction: 34.5
If the class-marks of a frequency distribution are 10.5, 16.5, 22.5, 28.5, 34.5, then the class-size is