Using the place value chart, we can see that the decimal 0.4 is four tenths so we can write 0.4 as the fraction 4 out of 10.
is not in lowest terms so we need to divide the numerator and the denominator by the greatest common factor of 4 and 10. The greatest common factor is 2.
Therefore, 0.4 can be written as the fraction
which is in lowest terms.