The answer depends on what the decimal number is. Three fifths of some unspecified quantity remains unspecified.
The decimal version of three fifths is .6 (six tenths is the same as three fifths).
It is: 3 and 3/5 = 3.6 as a decimal
3 and 2 fifths written in decimal form = 3.4
3/5 as a decimal is 0.6
3.6
It is: 3/5 = 0.6 as a decimal
3.2
It is 0.6
It is 2.6
3.0
It is: 1 and 3/5 = 1.6 as a decimal
3/5 (three-fifths)as a decimal = 0.6as a percentage = 60%3/5 = 0.6 = 60%