What is .4 as a fraction?

0.4 as a fraction is 4/10 or simplified as 2/5. This means that if you have 4 parts out of a total of 10 parts, it can also be represented as 2 parts out of 5 parts. The fraction 2/5 is in its simplest form because the numerator (2) and denominator (5) have no common factors other than 1.