Put these numbers in order of size, smallest first.
0.4 60% 1/5

Turn them all into one unit. like make all the numbers a decimal or a fraction.
Decimals:
0.4 is already a decimal but 60% and 1/5 are not. So, to turn any percent into a decimal, you move the decimal to the left two places (in other words, divide by 100) This would leave you with 0.4 (which you already had) and 0.6 (from the percent). 1/5 you can put into the calculator or you can think of it like a proportion. i.e. 1/5=x/10. 10 would be an easy number to use as it is easier to turn into a decimal. x would come out to be 2. So, 1/5=2/10. 2/10 would then come out to be 0.2 because any number over 10 you move the decimal left 1 place. This leaves you with 0.4, 0.6, and 0.2. From here it is easy to see that 0.2 is the smallest and 0.6 is the largest meaning, from least to greatest the answer would be: 1/5, 0.4, 60%.
Fractions:
You want to get all the numbers over the same denominator.1/5 is already a fraction so it's easier to get all the numbers to have a 5 in the denominator. To turn 60% into a fraction, all percents are the number over 100. So, 60% is 60/100. Simplify that to get 3/5. To get 0.4 into a fraction, all decimals after the point goes tenths hundreths and so on. The tenths are the number over 10, the hundreths is the number over 100 and so on. So, 0.4 is 4/10 but the denominator is not 5. To get 5 in the denominator, divide both the numerator and denominator by 2 to get 2/5. This leaves you with 2/5, 3/5, and 1/5. From here its easy to see that 1/5 is the least and 3/5 is the greatest.
So, the answer from least to greatest is 1/5, 0.4, 60%.