Place value continues below one
The first place to the right of the decimal point is tenths, followed by hundredths. Each place is one tenth of the place to its left. Thus 0.35 represents 35 hundredths.
Use equivalent units to calculate
Writing 0.4 as 0.40 makes its 40 hundredths visible. Aligning decimal points in addition and subtraction keeps tenths with tenths and hundredths with hundredths.
A mistake to avoid
More decimal digits do not necessarily mean a larger number. For example, 0.8 is greater than 0.75 because 80 hundredths is greater than 75 hundredths.
Worked example
Add 0.4 and 0.35
Rewrite 0.4 as 0.40. Add 40 hundredths and 35 hundredths to get 75 hundredths: 0.40 + 0.35 = 0.75. Adding zeros at the end of a decimal does not change its value.